google: remove legacy App Engine context stuff

Fixes #276

Change-Id: I3f2bed7201f2e6bb58913f3fae2e64287b9a66d5
Reviewed-on: https://go-review.googlesource.com/c/161959
Reviewed-by: Ross Light <light@google.com>
Reviewed-by: Jean de Klerk <deklerk@google.com>
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Author: bradfitz

README.md

@@ -19,57 +19,6 @@ See godoc for further documentation and examples.
 * [godoc.org/golang.org/x/oauth2](http://godoc.org/golang.org/x/oauth2)
 * [godoc.org/golang.org/x/oauth2/google](http://godoc.org/golang.org/x/oauth2/google)
 
-
-## App Engine
-
-In change 96e89be (March 2015), we removed the `oauth2.Context2` type in favor
-of the [`context.Context`](https://golang.org/x/net/context#Context) type from
-the `golang.org/x/net/context` package. Later replaced by the standard `context` package
-of the [`context.Context`](https://golang.org/pkg/context#Context) type.
-
-
-This means it's no longer possible to use the "Classic App Engine"
-`appengine.Context` type with the `oauth2` package. (You're using
-Classic App Engine if you import the package `"appengine"`.)
-
-To work around this, you may use the new `"google.golang.org/appengine"`
-package. This package has almost the same API as the `"appengine"` package,
-but it can be fetched with `go get` and used on "Managed VMs" and well as
-Classic App Engine.
-
-See the [new `appengine` package's readme](https://github.com/golang/appengine#updating-a-go-app-engine-app)
-for information on updating your app.
-
-If you don't want to update your entire app to use the new App Engine packages,
-you may use both sets of packages in parallel, using only the new packages
-with the `oauth2` package.
-
-```go
-import (
-	"context"
-	"golang.org/x/oauth2"
-	"golang.org/x/oauth2/google"
-	newappengine "google.golang.org/appengine"
-	newurlfetch "google.golang.org/appengine/urlfetch"
-
-	"appengine"
-)
-
-func handler(w http.ResponseWriter, r *http.Request) {
-	var c appengine.Context = appengine.NewContext(r)
-	c.Infof("Logging a message with the old package")
-
-	var ctx context.Context = newappengine.NewContext(r)
-	client := &http.Client{
-		Transport: &oauth2.Transport{
-			Source: google.AppEngineTokenSource(ctx, "scope"),
-			Base:   &newurlfetch.Transport{Context: ctx},
-		},
-	}
-	client.Get("...")
-}
-```
-
 ## Policy for new packages
 
 We no longer accept new provider-specific packages in this repo. For

google/example_test.go

@@ -14,8 +14,6 @@ import (
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
 	"golang.org/x/oauth2/jwt"
-	"google.golang.org/appengine"
-	"google.golang.org/appengine/urlfetch"
 )
 
 func ExampleDefaultClient() {
@@ -122,20 +120,6 @@ func Example_serviceAccount() {
 	client.Get("...")
 }
 
-func ExampleAppEngineTokenSource() {
-	var req *http.Request // from the ServeHTTP handler
-	ctx := appengine.NewContext(req)
-	client := &http.Client{
-		Transport: &oauth2.Transport{
-			Source: google.AppEngineTokenSource(ctx, "https://www.googleapis.com/auth/bigquery"),
-			Base: &urlfetch.Transport{
-				Context: ctx,
-			},
-		},
-	}
-	client.Get("...")
-}
-
 func ExampleComputeTokenSource() {
 	client := &http.Client{
 		Transport: &oauth2.Transport{