cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index 5b15a5a60f990de3f088e76bf89f5d903f41cd6b..1c4a8ab43c7393db4986f38198d9dfc5575019c8 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -5,6 +5,7 @@
 #include "cc/scheduler/scheduler.h"
 
 #include <algorithm>
+
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
@@ -32,8 +33,10 @@ BeginFrameSource* SchedulerFrameSourcesConstructor::ConstructPrimaryFrameSource(
     TRACE_EVENT1("cc",
                  "Scheduler::Scheduler()",
                  "PrimaryFrameSource",
-                 "SchedulerClient");
-    return scheduler->client_->ExternalBeginFrameSource();
+                 "ExternalBeginFrameSource");
+    DCHECK(scheduler->external_begin_frame_source_internal_.get());
+    scheduler->external_begin_frame_source_internal_->SetClientReady();
+    return scheduler->external_begin_frame_source_internal_.get();
   } else {
     TRACE_EVENT1("cc",
                  "Scheduler::Scheduler()",
@@ -73,12 +76,14 @@ Scheduler::Scheduler(
     const SchedulerSettings& scheduler_settings,
     int layer_tree_host_id,
     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+    scoped_refptr<ExternalBeginFrameSource> external_begin_frame_source,
     SchedulerFrameSourcesConstructor* frame_sources_constructor)
     : frame_source_(),
       primary_frame_source_(NULL),
       background_frame_source_(NULL),
       primary_frame_source_internal_(),
       background_frame_source_internal_(),
+      external_begin_frame_source_internal_(external_begin_frame_source),
       vsync_observer_(NULL),
       settings_(scheduler_settings),
       client_(client),
@@ -120,6 +125,8 @@ Scheduler::Scheduler(
 }
 
 Scheduler::~Scheduler() {
+  if (frame_source_->NeedsBeginFrames())
+    frame_source_->SetNeedsBeginFrames(false);
 }
 
 base::TimeTicks Scheduler::Now() const {