Add Context cancellation to clock.

common/clock/testclock/testtimer_test.go

Index: common/clock/testclock/testtimer_test.go
diff --git a/common/clock/testclock/testtimer_test.go b/common/clock/testclock/testtimer_test.go
index 90234e43ada67a3c9208c30444d22721c9b8e2a6..dccf1a8756a7cabe98ff1adf1c56cf13a09ad81c 100644
--- a/common/clock/testclock/testtimer_test.go
+++ b/common/clock/testclock/testtimer_test.go
@@ -9,6 +9,8 @@ import (
 	"time"
 
 	"github.com/luci/luci-go/common/clock"
+	"golang.org/x/net/context"
+
 	. "github.com/smartystreets/goconvey/convey"
 )
 
@@ -16,14 +18,15 @@ func TestTestTimer(t *testing.T) {
 	t.Parallel()
 
 	Convey(`A testing clock instance`, t, func() {
-		now := time.Date(2015, 01, 01, 00, 00, 00, 00, time.UTC)
+		ctx := context.Background()
+		now := TestTimeLocal
 		c := New(now)
 
 		Convey(`A timer instance`, func() {
-			t := c.NewTimer()
+			t := c.NewTimer(ctx)
 
 			Convey(`Should have a non-nil C.`, func() {
-				So(t.GetC(), ShouldBeNil)
+				So(t.GetC(), ShouldNotBeNil)
 			})
 
 			Convey(`When activated`, func() {
@@ -36,11 +39,11 @@ func TestTestTimer(t *testing.T) {
 
 				Convey(`When stopped, should return active.`, func() {
 					So(t.Stop(), ShouldBeTrue)
-					So(t.GetC(), ShouldBeNil)
+					So(t.GetC(), ShouldNotBeNil)
 
 					Convey(`And when stopped again, should return inactive.`, func() {
 						So(t.Stop(), ShouldBeFalse)
-						So(t.GetC(), ShouldBeNil)
+						So(t.GetC(), ShouldNotBeNil)
 					})
 				})
 
@@ -63,12 +66,11 @@ func TestTestTimer(t *testing.T) {
 				So(t.Reset(1*time.Second), ShouldBeFalse)
 				c.Add(1 * time.Second)
 
-				So(t.GetC(), ShouldNotBeNil)
-				So(<-t.GetC(), ShouldResemble, now.Add(1*time.Second))
+				So(<-t.GetC(), ShouldResemble, clock.TimerResult{Time: now.Add(1 * time.Second)})
 			})
 		})
 
-		Convey(`Multiple goroutines using the timer...`, func() {
+		Convey(`Multiple goroutines using timers...`, func() {
 			// Mark when timers are started, so we can ensure that our signalling
 			// happens after the timers have been instantiated.
 			timerStartedC := make(chan bool)
@@ -76,10 +78,10 @@ func TestTestTimer(t *testing.T) {
 				timerStartedC <- true
 			})
 
-			resultC := make(chan time.Time)
+			resultC := make(chan clock.TimerResult)
 			for i := time.Duration(0); i < 5; i++ {
 				go func(d time.Duration) {
-					timer := c.NewTimer()
+					timer := c.NewTimer(ctx)
 					timer.Reset(d)
 					resultC <- <-timer.GetC()
 				}(i * time.Second)