cc: Add readback and forced draw states to the Scheduler

cc/trees/thread_proxy.h

Index: cc/trees/thread_proxy.h
diff --git a/cc/trees/thread_proxy.h b/cc/trees/thread_proxy.h
index 76138a659393e2b9819e7ef3c9f37add45b304e7..56f8afbc217d35561eeb40523107bfbb32f9624f 100644
--- a/cc/trees/thread_proxy.h
+++ b/cc/trees/thread_proxy.h
@@ -95,10 +95,10 @@ class ThreadProxy : public Proxy,
   // SchedulerClient implementation
   virtual void SetNeedsBeginFrameOnImplThread(bool enable) OVERRIDE;
   virtual void ScheduledActionSendBeginFrameToMainThread() OVERRIDE;
-  virtual ScheduledActionDrawAndSwapResult
-      ScheduledActionDrawAndSwapIfPossible() OVERRIDE;
-  virtual ScheduledActionDrawAndSwapResult ScheduledActionDrawAndSwapForced()
+  virtual DrawSwapReadbackResult ScheduledActionDrawAndSwapIfPossible()
       OVERRIDE;
+  virtual DrawSwapReadbackResult ScheduledActionDrawAndSwapForced() OVERRIDE;
+  virtual DrawSwapReadbackResult ScheduledActionDrawAndReadback() OVERRIDE;
   virtual void ScheduledActionCommit() OVERRIDE;
   virtual void ScheduledActionUpdateVisibleTiles() OVERRIDE;
   virtual void ScheduledActionActivatePendingTree() OVERRIDE;
@@ -144,7 +144,9 @@ class ThreadProxy : public Proxy,
   struct CommitPendingRequest;
   struct SchedulerStateRequest;
 
-  void ForceCommitOnImplThread(CompletionEvent* completion);
+  void ForceCommitForReadbackOnImplThread(
+      CompletionEvent* begin_frame_sent_completion,
+      ReadbackRequest* request);
   void StartCommitOnImplThread(
       CompletionEvent* completion,
       ResourceUpdateQueue* queue,
@@ -168,8 +170,9 @@ class ThreadProxy : public Proxy,
   void LayerTreeHostClosedOnImplThread(CompletionEvent* completion);
   void AcquireLayerTexturesForMainThreadOnImplThread(
       CompletionEvent* completion);
-  ScheduledActionDrawAndSwapResult ScheduledActionDrawAndSwapInternal(
-      bool forced_draw);
+  DrawSwapReadbackResult DrawSwapReadbackInternal(bool forced_draw,
+                                                  bool swap_requested,
+                                                  bool readback_requested);
   void ForceSerializeOnSwapBuffersOnImplThread(CompletionEvent* completion);
   void CheckOutputSurfaceStatusOnImplThread();
   void CommitPendingOnImplThreadForTesting(CommitPendingRequest* request);