diff --git a/vendor/google.golang.org/appengine/internal/api.go b/vendor/google.golang.org/appengine/internal/api.go
new file mode 100644
index 0000000..a6ec19e
--- /dev/null
+++ b/vendor/google.golang.org/appengine/internal/api.go
@@ -0,0 +1,675 @@
+// Copyright 2011 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+
+package internal
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/golang/protobuf/proto"
+	netcontext "golang.org/x/net/context"
+
+	basepb "google.golang.org/appengine/internal/base"
+	logpb "google.golang.org/appengine/internal/log"
+	remotepb "google.golang.org/appengine/internal/remote_api"
+)
+
+const (
+	apiPath             = "/rpc_http"
+	defaultTicketSuffix = "/default.20150612t184001.0"
+)
+
+var (
+	// Incoming headers.
+	ticketHeader       = http.CanonicalHeaderKey("X-AppEngine-API-Ticket")
+	dapperHeader       = http.CanonicalHeaderKey("X-Google-DapperTraceInfo")
+	traceHeader        = http.CanonicalHeaderKey("X-Cloud-Trace-Context")
+	curNamespaceHeader = http.CanonicalHeaderKey("X-AppEngine-Current-Namespace")
+	userIPHeader       = http.CanonicalHeaderKey("X-AppEngine-User-IP")
+	remoteAddrHeader   = http.CanonicalHeaderKey("X-AppEngine-Remote-Addr")
+	devRequestIdHeader = http.CanonicalHeaderKey("X-Appengine-Dev-Request-Id")
+
+	// Outgoing headers.
+	apiEndpointHeader      = http.CanonicalHeaderKey("X-Google-RPC-Service-Endpoint")
+	apiEndpointHeaderValue = []string{"app-engine-apis"}
+	apiMethodHeader        = http.CanonicalHeaderKey("X-Google-RPC-Service-Method")
+	apiMethodHeaderValue   = []string{"/VMRemoteAPI.CallRemoteAPI"}
+	apiDeadlineHeader      = http.CanonicalHeaderKey("X-Google-RPC-Service-Deadline")
+	apiContentType         = http.CanonicalHeaderKey("Content-Type")
+	apiContentTypeValue    = []string{"application/octet-stream"}
+	logFlushHeader         = http.CanonicalHeaderKey("X-AppEngine-Log-Flush-Count")
+
+	apiHTTPClient = &http.Client{
+		Transport: &http.Transport{
+			Proxy: http.ProxyFromEnvironment,
+			Dial:  limitDial,
+		},
+	}
+
+	defaultTicketOnce     sync.Once
+	defaultTicket         string
+	backgroundContextOnce sync.Once
+	backgroundContext     netcontext.Context
+)
+
+func apiURL() *url.URL {
+	host, port := "appengine.googleapis.internal", "10001"
+	if h := os.Getenv("API_HOST"); h != "" {
+		host = h
+	}
+	if p := os.Getenv("API_PORT"); p != "" {
+		port = p
+	}
+	return &url.URL{
+		Scheme: "http",
+		Host:   host + ":" + port,
+		Path:   apiPath,
+	}
+}
+
+func handleHTTP(w http.ResponseWriter, r *http.Request) {
+	c := &context{
+		req:       r,
+		outHeader: w.Header(),
+		apiURL:    apiURL(),
+	}
+	r = r.WithContext(withContext(r.Context(), c))
+	c.req = r
+
+	stopFlushing := make(chan int)
+
+	// Patch up RemoteAddr so it looks reasonable.
+	if addr := r.Header.Get(userIPHeader); addr != "" {
+		r.RemoteAddr = addr
+	} else if addr = r.Header.Get(remoteAddrHeader); addr != "" {
+		r.RemoteAddr = addr
+	} else {
+		// Should not normally reach here, but pick a sensible default anyway.
+		r.RemoteAddr = "127.0.0.1"
+	}
+	// The address in the headers will most likely be of these forms:
+	//	123.123.123.123
+	//	2001:db8::1
+	// net/http.Request.RemoteAddr is specified to be in "IP:port" form.
+	if _, _, err := net.SplitHostPort(r.RemoteAddr); err != nil {
+		// Assume the remote address is only a host; add a default port.
+		r.RemoteAddr = net.JoinHostPort(r.RemoteAddr, "80")
+	}
+
+	// Start goroutine responsible for flushing app logs.
+	// This is done after adding c to ctx.m (and stopped before removing it)
+	// because flushing logs requires making an API call.
+	go c.logFlusher(stopFlushing)
+
+	executeRequestSafely(c, r)
+	c.outHeader = nil // make sure header changes aren't respected any more
+
+	stopFlushing <- 1 // any logging beyond this point will be dropped
+
+	// Flush any pending logs asynchronously.
+	c.pendingLogs.Lock()
+	flushes := c.pendingLogs.flushes
+	if len(c.pendingLogs.lines) > 0 {
+		flushes++
+	}
+	c.pendingLogs.Unlock()
+	flushed := make(chan struct{})
+	go func() {
+		defer close(flushed)
+		// Force a log flush, because with very short requests we
+		// may not ever flush logs.
+		c.flushLog(true)
+	}()
+	w.Header().Set(logFlushHeader, strconv.Itoa(flushes))
+
+	// Avoid nil Write call if c.Write is never called.
+	if c.outCode != 0 {
+		w.WriteHeader(c.outCode)
+	}
+	if c.outBody != nil {
+		w.Write(c.outBody)
+	}
+	// Wait for the last flush to complete before returning,
+	// otherwise the security ticket will not be valid.
+	<-flushed
+}
+
+func executeRequestSafely(c *context, r *http.Request) {
+	defer func() {
+		if x := recover(); x != nil {
+			logf(c, 4, "%s", renderPanic(x)) // 4 == critical
+			c.outCode = 500
+		}
+	}()
+
+	http.DefaultServeMux.ServeHTTP(c, r)
+}
+
+func renderPanic(x interface{}) string {
+	buf := make([]byte, 16<<10) // 16 KB should be plenty
+	buf = buf[:runtime.Stack(buf, false)]
+
+	// Remove the first few stack frames:
+	//   this func
+	//   the recover closure in the caller
+	// That will root the stack trace at the site of the panic.
+	const (
+		skipStart  = "internal.renderPanic"
+		skipFrames = 2
+	)
+	start := bytes.Index(buf, []byte(skipStart))
+	p := start
+	for i := 0; i < skipFrames*2 && p+1 < len(buf); i++ {
+		p = bytes.IndexByte(buf[p+1:], '\n') + p + 1
+		if p < 0 {
+			break
+		}
+	}
+	if p >= 0 {
+		// buf[start:p+1] is the block to remove.
+		// Copy buf[p+1:] over buf[start:] and shrink buf.
+		copy(buf[start:], buf[p+1:])
+		buf = buf[:len(buf)-(p+1-start)]
+	}
+
+	// Add panic heading.
+	head := fmt.Sprintf("panic: %v\n\n", x)
+	if len(head) > len(buf) {
+		// Extremely unlikely to happen.
+		return head
+	}
+	copy(buf[len(head):], buf)
+	copy(buf, head)
+
+	return string(buf)
+}
+
+// context represents the context of an in-flight HTTP request.
+// It implements the appengine.Context and http.ResponseWriter interfaces.
+type context struct {
+	req *http.Request
+
+	outCode   int
+	outHeader http.Header
+	outBody   []byte
+
+	pendingLogs struct {
+		sync.Mutex
+		lines   []*logpb.UserAppLogLine
+		flushes int
+	}
+
+	apiURL *url.URL
+}
+
+var contextKey = "holds a *context"
+
+// jointContext joins two contexts in a superficial way.
+// It takes values and timeouts from a base context, and only values from another context.
+type jointContext struct {
+	base       netcontext.Context
+	valuesOnly netcontext.Context
+}
+
+func (c jointContext) Deadline() (time.Time, bool) {
+	return c.base.Deadline()
+}
+
+func (c jointContext) Done() <-chan struct{} {
+	return c.base.Done()
+}
+
+func (c jointContext) Err() error {
+	return c.base.Err()
+}
+
+func (c jointContext) Value(key interface{}) interface{} {
+	if val := c.base.Value(key); val != nil {
+		return val
+	}
+	return c.valuesOnly.Value(key)
+}
+
+// fromContext returns the App Engine context or nil if ctx is not
+// derived from an App Engine context.
+func fromContext(ctx netcontext.Context) *context {
+	c, _ := ctx.Value(&contextKey).(*context)
+	return c
+}
+
+func withContext(parent netcontext.Context, c *context) netcontext.Context {
+	ctx := netcontext.WithValue(parent, &contextKey, c)
+	if ns := c.req.Header.Get(curNamespaceHeader); ns != "" {
+		ctx = withNamespace(ctx, ns)
+	}
+	return ctx
+}
+
+func toContext(c *context) netcontext.Context {
+	return withContext(netcontext.Background(), c)
+}
+
+func IncomingHeaders(ctx netcontext.Context) http.Header {
+	if c := fromContext(ctx); c != nil {
+		return c.req.Header
+	}
+	return nil
+}
+
+func ReqContext(req *http.Request) netcontext.Context {
+	return req.Context()
+}
+
+func WithContext(parent netcontext.Context, req *http.Request) netcontext.Context {
+	return jointContext{
+		base:       parent,
+		valuesOnly: req.Context(),
+	}
+}
+
+// DefaultTicket returns a ticket used for background context or dev_appserver.
+func DefaultTicket() string {
+	defaultTicketOnce.Do(func() {
+		if IsDevAppServer() {
+			defaultTicket = "testapp" + defaultTicketSuffix
+			return
+		}
+		appID := partitionlessAppID()
+		escAppID := strings.Replace(strings.Replace(appID, ":", "_", -1), ".", "_", -1)
+		majVersion := VersionID(nil)
+		if i := strings.Index(majVersion, "."); i > 0 {
+			majVersion = majVersion[:i]
+		}
+		defaultTicket = fmt.Sprintf("%s/%s.%s.%s", escAppID, ModuleName(nil), majVersion, InstanceID())
+	})
+	return defaultTicket
+}
+
+func BackgroundContext() netcontext.Context {
+	backgroundContextOnce.Do(func() {
+		// Compute background security ticket.
+		ticket := DefaultTicket()
+
+		c := &context{
+			req: &http.Request{
+				Header: http.Header{
+					ticketHeader: []string{ticket},
+				},
+			},
+			apiURL: apiURL(),
+		}
+		backgroundContext = toContext(c)
+
+		// TODO(dsymonds): Wire up the shutdown handler to do a final flush.
+		go c.logFlusher(make(chan int))
+	})
+
+	return backgroundContext
+}
+
+// RegisterTestRequest registers the HTTP request req for testing, such that
+// any API calls are sent to the provided URL. It returns a closure to delete
+// the registration.
+// It should only be used by aetest package.
+func RegisterTestRequest(req *http.Request, apiURL *url.URL, decorate func(netcontext.Context) netcontext.Context) (*http.Request, func()) {
+	c := &context{
+		req:    req,
+		apiURL: apiURL,
+	}
+	ctx := withContext(decorate(req.Context()), c)
+	req = req.WithContext(ctx)
+	c.req = req
+	return req, func() {}
+}
+
+var errTimeout = &CallError{
+	Detail:  "Deadline exceeded",
+	Code:    int32(remotepb.RpcError_CANCELLED),
+	Timeout: true,
+}
+
+func (c *context) Header() http.Header { return c.outHeader }
+
+// Copied from $GOROOT/src/pkg/net/http/transfer.go. Some response status
+// codes do not permit a response body (nor response entity headers such as
+// Content-Length, Content-Type, etc).
+func bodyAllowedForStatus(status int) bool {
+	switch {
+	case status >= 100 && status <= 199:
+		return false
+	case status == 204:
+		return false
+	case status == 304:
+		return false
+	}
+	return true
+}
+
+func (c *context) Write(b []byte) (int, error) {
+	if c.outCode == 0 {
+		c.WriteHeader(http.StatusOK)
+	}
+	if len(b) > 0 && !bodyAllowedForStatus(c.outCode) {
+		return 0, http.ErrBodyNotAllowed
+	}
+	c.outBody = append(c.outBody, b...)
+	return len(b), nil
+}
+
+func (c *context) WriteHeader(code int) {
+	if c.outCode != 0 {
+		logf(c, 3, "WriteHeader called multiple times on request.") // error level
+		return
+	}
+	c.outCode = code
+}
+
+func (c *context) post(body []byte, timeout time.Duration) (b []byte, err error) {
+	hreq := &http.Request{
+		Method: "POST",
+		URL:    c.apiURL,
+		Header: http.Header{
+			apiEndpointHeader: apiEndpointHeaderValue,
+			apiMethodHeader:   apiMethodHeaderValue,
+			apiContentType:    apiContentTypeValue,
+			apiDeadlineHeader: []string{strconv.FormatFloat(timeout.Seconds(), 'f', -1, 64)},
+		},
+		Body:          ioutil.NopCloser(bytes.NewReader(body)),
+		ContentLength: int64(len(body)),
+		Host:          c.apiURL.Host,
+	}
+	if info := c.req.Header.Get(dapperHeader); info != "" {
+		hreq.Header.Set(dapperHeader, info)
+	}
+	if info := c.req.Header.Get(traceHeader); info != "" {
+		hreq.Header.Set(traceHeader, info)
+	}
+
+	tr := apiHTTPClient.Transport.(*http.Transport)
+
+	var timedOut int32 // atomic; set to 1 if timed out
+	t := time.AfterFunc(timeout, func() {
+		atomic.StoreInt32(&timedOut, 1)
+		tr.CancelRequest(hreq)
+	})
+	defer t.Stop()
+	defer func() {
+		// Check if timeout was exceeded.
+		if atomic.LoadInt32(&timedOut) != 0 {
+			err = errTimeout
+		}
+	}()
+
+	hresp, err := apiHTTPClient.Do(hreq)
+	if err != nil {
+		return nil, &CallError{
+			Detail: fmt.Sprintf("service bridge HTTP failed: %v", err),
+			Code:   int32(remotepb.RpcError_UNKNOWN),
+		}
+	}
+	defer hresp.Body.Close()
+	hrespBody, err := ioutil.ReadAll(hresp.Body)
+	if hresp.StatusCode != 200 {
+		return nil, &CallError{
+			Detail: fmt.Sprintf("service bridge returned HTTP %d (%q)", hresp.StatusCode, hrespBody),
+			Code:   int32(remotepb.RpcError_UNKNOWN),
+		}
+	}
+	if err != nil {
+		return nil, &CallError{
+			Detail: fmt.Sprintf("service bridge response bad: %v", err),
+			Code:   int32(remotepb.RpcError_UNKNOWN),
+		}
+	}
+	return hrespBody, nil
+}
+
+func Call(ctx netcontext.Context, service, method string, in, out proto.Message) error {
+	if ns := NamespaceFromContext(ctx); ns != "" {
+		if fn, ok := NamespaceMods[service]; ok {
+			fn(in, ns)
+		}
+	}
+
+	if f, ctx, ok := callOverrideFromContext(ctx); ok {
+		return f(ctx, service, method, in, out)
+	}
+
+	// Handle already-done contexts quickly.
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	default:
+	}
+
+	c := fromContext(ctx)
+	if c == nil {
+		// Give a good error message rather than a panic lower down.
+		return errNotAppEngineContext
+	}
+
+	// Apply transaction modifications if we're in a transaction.
+	if t := transactionFromContext(ctx); t != nil {
+		if t.finished {
+			return errors.New("transaction context has expired")
+		}
+		applyTransaction(in, &t.transaction)
+	}
+
+	// Default RPC timeout is 60s.
+	timeout := 60 * time.Second
+	if deadline, ok := ctx.Deadline(); ok {
+		timeout = deadline.Sub(time.Now())
+	}
+
+	data, err := proto.Marshal(in)
+	if err != nil {
+		return err
+	}
+
+	ticket := c.req.Header.Get(ticketHeader)
+	// Use a test ticket under test environment.
+	if ticket == "" {
+		if appid := ctx.Value(&appIDOverrideKey); appid != nil {
+			ticket = appid.(string) + defaultTicketSuffix
+		}
+	}
+	// Fall back to use background ticket when the request ticket is not available in Flex or dev_appserver.
+	if ticket == "" {
+		ticket = DefaultTicket()
+	}
+	if dri := c.req.Header.Get(devRequestIdHeader); IsDevAppServer() && dri != "" {
+		ticket = dri
+	}
+	req := &remotepb.Request{
+		ServiceName: &service,
+		Method:      &method,
+		Request:     data,
+		RequestId:   &ticket,
+	}
+	hreqBody, err := proto.Marshal(req)
+	if err != nil {
+		return err
+	}
+
+	hrespBody, err := c.post(hreqBody, timeout)
+	if err != nil {
+		return err
+	}
+
+	res := &remotepb.Response{}
+	if err := proto.Unmarshal(hrespBody, res); err != nil {
+		return err
+	}
+	if res.RpcError != nil {
+		ce := &CallError{
+			Detail: res.RpcError.GetDetail(),
+			Code:   *res.RpcError.Code,
+		}
+		switch remotepb.RpcError_ErrorCode(ce.Code) {
+		case remotepb.RpcError_CANCELLED, remotepb.RpcError_DEADLINE_EXCEEDED:
+			ce.Timeout = true
+		}
+		return ce
+	}
+	if res.ApplicationError != nil {
+		return &APIError{
+			Service: *req.ServiceName,
+			Detail:  res.ApplicationError.GetDetail(),
+			Code:    *res.ApplicationError.Code,
+		}
+	}
+	if res.Exception != nil || res.JavaException != nil {
+		// This shouldn't happen, but let's be defensive.
+		return &CallError{
+			Detail: "service bridge returned exception",
+			Code:   int32(remotepb.RpcError_UNKNOWN),
+		}
+	}
+	return proto.Unmarshal(res.Response, out)
+}
+
+func (c *context) Request() *http.Request {
+	return c.req
+}
+
+func (c *context) addLogLine(ll *logpb.UserAppLogLine) {
+	// Truncate long log lines.
+	// TODO(dsymonds): Check if this is still necessary.
+	const lim = 8 << 10
+	if len(*ll.Message) > lim {
+		suffix := fmt.Sprintf("...(length %d)", len(*ll.Message))
+		ll.Message = proto.String((*ll.Message)[:lim-len(suffix)] + suffix)
+	}
+
+	c.pendingLogs.Lock()
+	c.pendingLogs.lines = append(c.pendingLogs.lines, ll)
+	c.pendingLogs.Unlock()
+}
+
+var logLevelName = map[int64]string{
+	0: "DEBUG",
+	1: "INFO",
+	2: "WARNING",
+	3: "ERROR",
+	4: "CRITICAL",
+}
+
+func logf(c *context, level int64, format string, args ...interface{}) {
+	if c == nil {
+		panic("not an App Engine context")
+	}
+	s := fmt.Sprintf(format, args...)
+	s = strings.TrimRight(s, "\n") // Remove any trailing newline characters.
+	c.addLogLine(&logpb.UserAppLogLine{
+		TimestampUsec: proto.Int64(time.Now().UnixNano() / 1e3),
+		Level:         &level,
+		Message:       &s,
+	})
+	// Only duplicate log to stderr if not running on App Engine second generation
+	if !IsSecondGen() {
+		log.Print(logLevelName[level] + ": " + s)
+	}
+}
+
+// flushLog attempts to flush any pending logs to the appserver.
+// It should not be called concurrently.
+func (c *context) flushLog(force bool) (flushed bool) {
+	c.pendingLogs.Lock()
+	// Grab up to 30 MB. We can get away with up to 32 MB, but let's be cautious.
+	n, rem := 0, 30<<20
+	for ; n < len(c.pendingLogs.lines); n++ {
+		ll := c.pendingLogs.lines[n]
+		// Each log line will require about 3 bytes of overhead.
+		nb := proto.Size(ll) + 3
+		if nb > rem {
+			break
+		}
+		rem -= nb
+	}
+	lines := c.pendingLogs.lines[:n]
+	c.pendingLogs.lines = c.pendingLogs.lines[n:]
+	c.pendingLogs.Unlock()
+
+	if len(lines) == 0 && !force {
+		// Nothing to flush.
+		return false
+	}
+
+	rescueLogs := false
+	defer func() {
+		if rescueLogs {
+			c.pendingLogs.Lock()
+			c.pendingLogs.lines = append(lines, c.pendingLogs.lines...)
+			c.pendingLogs.Unlock()
+		}
+	}()
+
+	buf, err := proto.Marshal(&logpb.UserAppLogGroup{
+		LogLine: lines,
+	})
+	if err != nil {
+		log.Printf("internal.flushLog: marshaling UserAppLogGroup: %v", err)
+		rescueLogs = true
+		return false
+	}
+
+	req := &logpb.FlushRequest{
+		Logs: buf,
+	}
+	res := &basepb.VoidProto{}
+	c.pendingLogs.Lock()
+	c.pendingLogs.flushes++
+	c.pendingLogs.Unlock()
+	if err := Call(toContext(c), "logservice", "Flush", req, res); err != nil {
+		log.Printf("internal.flushLog: Flush RPC: %v", err)
+		rescueLogs = true
+		return false
+	}
+	return true
+}
+
+const (
+	// Log flushing parameters.
+	flushInterval      = 1 * time.Second
+	forceFlushInterval = 60 * time.Second
+)
+
+func (c *context) logFlusher(stop <-chan int) {
+	lastFlush := time.Now()
+	tick := time.NewTicker(flushInterval)
+	for {
+		select {
+		case <-stop:
+			// Request finished.
+			tick.Stop()
+			return
+		case <-tick.C:
+			force := time.Now().Sub(lastFlush) > forceFlushInterval
+			if c.flushLog(force) {
+				lastFlush = time.Now()
+			}
+		}
+	}
+}
+
+func ContextForTesting(req *http.Request) netcontext.Context {
+	return toContext(&context{req: req})
+}