Use message passing for BeginFrameAndCommitState and clean up forced commit logic

cc/scheduler_state_machine.cc

Index: cc/scheduler_state_machine.cc
diff --git a/cc/scheduler_state_machine.cc b/cc/scheduler_state_machine.cc
index d0a3577074748461f950e92409b293fc7b8fcbee..f70d1ad9e76f499df4ad0ee3114272c7cb8df76a 100644
--- a/cc/scheduler_state_machine.cc
+++ b/cc/scheduler_state_machine.cc
@@ -21,6 +21,7 @@ SchedulerStateMachine::SchedulerStateMachine()
     , m_needsForcedRedrawAfterNextCommit(false)
     , m_needsCommit(false)
     , m_needsForcedCommit(false)
+    , m_expectImmediateBeginFrame(false)
     , m_mainThreadNeedsLayerTextures(false)
     , m_insideVSync(false)
     , m_visible(false)
@@ -45,6 +46,7 @@ std::string SchedulerStateMachine::toString()
     base::StringAppendF(&str, "m_needsForcedRedrawAfterNextCommit = %d; ", m_needsForcedRedrawAfterNextCommit);
     base::StringAppendF(&str, "m_needsCommit = %d; ", m_needsCommit);
     base::StringAppendF(&str, "m_needsForcedCommit = %d; ", m_needsForcedCommit);
+    base::StringAppendF(&str, "m_expectImmediateBeginFrame = %d; ", m_expectImmediateBeginFrame);
     base::StringAppendF(&str, "m_mainThreadNeedsLayerTextures = %d; ", m_mainThreadNeedsLayerTextures);
     base::StringAppendF(&str, "m_insideVSync = %d; ", m_insideVSync);
     base::StringAppendF(&str, "m_visible = %d; ", m_visible);
@@ -189,8 +191,13 @@ void SchedulerStateMachine::updateState(Action action)
         m_drawIfPossibleFailed = false;
         if (m_insideVSync)
             m_lastFrameNumberWhereDrawWasCalled = m_currentFrameNumber;
-        if (m_commitState == COMMIT_STATE_WAITING_FOR_FIRST_DRAW)
-            m_commitState = COMMIT_STATE_IDLE;
+        if (m_commitState == COMMIT_STATE_WAITING_FOR_FIRST_DRAW) {
+            if (m_expectImmediateBeginFrame) {
+                m_commitState = COMMIT_STATE_FRAME_IN_PROGRESS;
+                m_expectImmediateBeginFrame = false;
+            } else
+                m_commitState = COMMIT_STATE_IDLE;
+        }
         if (m_textureState == LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD)
             m_textureState = LAYER_TEXTURE_STATE_UNLOCKED;
         return;
@@ -280,19 +287,25 @@ void SchedulerStateMachine::setNeedsCommit()
 void SchedulerStateMachine::setNeedsForcedCommit()
 {
     m_needsForcedCommit = true;
+    m_expectImmediateBeginFrame = true;
 }
 
 void SchedulerStateMachine::beginFrameComplete()
 {
-    DCHECK(m_commitState == COMMIT_STATE_FRAME_IN_PROGRESS);
+    DCHECK(m_commitState == COMMIT_STATE_FRAME_IN_PROGRESS ||
+           (m_expectImmediateBeginFrame && m_commitState != COMMIT_STATE_IDLE)) << toString();
     m_commitState = COMMIT_STATE_READY_TO_COMMIT;
 }
 
 void SchedulerStateMachine::beginFrameAborted()
 {
     DCHECK(m_commitState == COMMIT_STATE_FRAME_IN_PROGRESS);
-    m_commitState = COMMIT_STATE_IDLE;
-    setNeedsCommit();
+    if (m_expectImmediateBeginFrame)
+        m_expectImmediateBeginFrame = false;
+    else {
+        m_commitState = COMMIT_STATE_IDLE;
+        setNeedsCommit();
+    }
 }
 
 void SchedulerStateMachine::didLoseContext()