Add Context cancellation to clock.

common/clock/external.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package clock
 
 import (
         "time"
 
         "golang.org/x/net/context"
@@ skipping 32 matching lines @@
         return
 }
 
 // Now calls Clock.Now on the Clock instance stored in the supplied Context.
 func Now(ctx context.Context) time.Time {
         return Get(ctx).Now()
 }
 
 // Sleep calls Clock.Sleep on the Clock instance stored in the supplied Context.
 func Sleep(ctx context.Context, d time.Duration) {
-        Get(ctx).Sleep(d)
+        Get(ctx).Sleep(ctx, d)
 }
 
 // NewTimer calls Clock.NewTimer on the Clock instance stored in the supplied
 // Context.
 func NewTimer(ctx context.Context) Timer {
-        return Get(ctx).NewTimer()
+        return Get(ctx).NewTimer(ctx)
 }
 
 // After calls Clock.After on the Clock instance stored in the supplied Context.
-func After(ctx context.Context, d time.Duration) <-chan time.Time {
-        return Get(ctx).After(d)
+func After(ctx context.Context, d time.Duration) <-chan AfterResult {
+        return Get(ctx).After(ctx, d)
 }