cc: Making BeginFrameSources support multiple BeginFrameObservers.

cc/scheduler/begin_frame_source_unittest.cc

Index: cc/scheduler/begin_frame_source_unittest.cc
diff --git a/cc/scheduler/begin_frame_source_unittest.cc b/cc/scheduler/begin_frame_source_unittest.cc
index 1f85622878e91680efd7f5ea56402c3653d81ada..a08e907eb85f2128ed02b619421d5b6c2d7979fd 100644
--- a/cc/scheduler/begin_frame_source_unittest.cc
+++ b/cc/scheduler/begin_frame_source_unittest.cc
@@ -231,9 +231,6 @@ TEST(BeginFrameSourceBaseTest, ObserverManipulation) {
   EXPECT_EQ(&obs, source.GetObserver());
 
 #ifndef NDEBUG
-  // Adding an observer when an observer already exists should DCHECK fail.
-  EXPECT_DEATH({ source.AddObserver(&otherObs); }, "");
-
   // Removing wrong observer should DCHECK fail.
   EXPECT_DEATH({ source.RemoveObserver(&otherObs); }, "");
 
@@ -249,6 +246,8 @@ TEST(BeginFrameSourceBaseTest, ObserverManipulation) {
   source.AddObserver(&otherObs);
   EXPECT_EQ(&otherObs, source.GetObserver());
   source.RemoveObserver(&otherObs);
+
+  // TODO(mithro): Add a test here for adding / removing multiple observers.
 }
 
 TEST(BeginFrameSourceBaseTest, Observer) {