Revert of cc: SwapAck throttle Swap without throttling MainFrames...

Revert of cc: SwapAck throttle Swap without throttling MainFrames (https://codereview.chromium.org/222023010/)

Reason for revert:
[Sheriff] Speculative revert for breaking win7 dbg:

http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%284%29/builds/26034

Will reland if it didn't help.

Original issue's description:
> cc: SwapAck throttle Swap without throttling MainFrames
> 
> This should improve main thread throughput in cases
> where we are deferring the BeginMainFrame, but don't
> really need to because the swap ack will come back
> before the impl thread needs to draw anyway.
> 
> BUG=311213
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266685

NOTREECHECKS=true
NOTRY=true
BUG=311213
TBR=Sami, danakj, brianderson

Review URL: https://codereview.chromium.org/255033004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266757 0039d316-1c4b-4281-b951-d872f2087c98

cc/scheduler/scheduler_state_machine.cc

@@ -502,6 +502,11 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (!HasInitializedOutputSurface())
     return false;
 
+  // SwapAck throttle the BeginMainFrames
+  // TODO(brianderson): Remove this restriction to improve throughput.
+  if (pending_swaps_ >= max_pending_swaps_)
+    return false;
+
   if (skip_begin_main_frame_to_reduce_latency_)
     return false;
 

cc/scheduler/scheduler_unittest.cc

@@ -1266,11 +1266,10 @@ TEST(SchedulerTest, BeginRetroFrame_SwapThrottled) {
   client.Reset();
 
   // While swap throttled, BeginRetroFrames should trigger BeginImplFrames
-  // and BeginMainFrames, but not draw.
+  // but not a BeginMainFrame or draw.
   scheduler->SetNeedsCommit();
   client.task_runner().RunPendingTasks();  // Run posted BeginRetroFrame.
-  EXPECT_ACTION("WillBeginImplFrame", client, 0, 2);
-  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client, 1, 2);
+  EXPECT_ACTION("WillBeginImplFrame", client, 0, 1);
   EXPECT_TRUE(scheduler->BeginImplFrameDeadlinePending());
   EXPECT_TRUE(client.needs_begin_frame());
   client.Reset();
@@ -1285,7 +1284,7 @@ TEST(SchedulerTest, BeginRetroFrame_SwapThrottled) {
 
   // Take us out of a swap throttled state.
   scheduler->DidSwapBuffersComplete();
-  EXPECT_EQ(0, client.num_actions_());
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client, 0, 1);
   EXPECT_TRUE(scheduler->BeginImplFrameDeadlinePending());
   EXPECT_TRUE(client.needs_begin_frame());
   client.Reset();
@@ -1442,19 +1441,18 @@ void BeginFramesNotFromClient_SwapThrottled(bool begin_frame_scheduling_enabled,
   EXPECT_FALSE(client.needs_begin_frame());
   client.Reset();
 
-  // While swap throttled, BeginFrames should trigger BeginImplFrame and
-  // BeginMainFrame, but not draw.
+  // While swap throttled, BeginFrames should trigger BeginImplFrames,
+  // but not a BeginMainFrame or draw.
   scheduler->SetNeedsCommit();
   client.task_runner().RunPendingTasks();  // Run posted BeginFrame.
-  EXPECT_ACTION("WillBeginImplFrame", client, 0, 2);
-  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client, 1, 2);
+  EXPECT_ACTION("WillBeginImplFrame", client, 0, 1);
   EXPECT_TRUE(scheduler->BeginImplFrameDeadlinePending());
   EXPECT_FALSE(client.needs_begin_frame());
   client.Reset();
 
   // Take us out of a swap throttled state.
   scheduler->DidSwapBuffersComplete();
-  EXPECT_EQ(0, client.num_actions_());
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client, 0, 1);
   EXPECT_TRUE(scheduler->BeginImplFrameDeadlinePending());
   EXPECT_FALSE(client.needs_begin_frame());
   client.Reset();