cc: Making BeginFrameSources support multiple BeginFrameObservers.

cc/test/scheduler_test_common.h

 // Copyright 2011 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.
 
 #ifndef CC_TEST_SCHEDULER_TEST_COMMON_H_
 #define CC_TEST_SCHEDULER_TEST_COMMON_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 74 matching lines @@
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TestDelayBasedTimeSource);
 };
 
 class FakeBeginFrameSource : public BeginFrameSourceBase {
  public:
   FakeBeginFrameSource() : remaining_frames_(false) {}
   ~FakeBeginFrameSource() override {}
 
-  BeginFrameObserver* GetObserver() { return observer_; }
+  BeginFrameObserver* GetObserver() {
+    if ((observer_list_).might_have_observers()) {
+      base::ObserverList<BeginFrameObserver>::Iterator it(&observer_list_);
+      BeginFrameObserver* obs;
+      while ((obs = it.GetNext()) != nullptr) {
+        return obs;
+      }
+    }
+    return nullptr;
+  }
 
   BeginFrameArgs TestLastUsedBeginFrameArgs() {
-    if (observer_) {
-      return observer_->LastUsedBeginFrameArgs();
+    BeginFrameObserver* obs = GetObserver();
+    if (obs) {
+      return obs->LastUsedBeginFrameArgs();
     }
     return BeginFrameArgs();
   }
 
   void TestOnBeginFrame(const BeginFrameArgs& args) {
     return CallOnBeginFrame(args);
   }
 
   // BeginFrameSource
   void DidFinishFrame(size_t remaining_frames) override;
@@ skipping 141 matching lines @@
       scoped_ptr<CompositorTimingHistory> compositor_timing_history);
 
   base::SimpleTestTickClock* now_src_;
 
   DISALLOW_COPY_AND_ASSIGN(TestScheduler);
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_SCHEDULER_TEST_COMMON_H_