Mac: Add more trace events for CAOpenGLLayers

ui/accelerated_widget_mac/io_surface_layer.mm

 // Copyright 2013 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.
 
 #include "ui/accelerated_widget_mac/io_surface_layer.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 #include <OpenGL/CGLIOSurface.h>
 #include <OpenGL/CGLRenderers.h>
 #include <OpenGL/gl.h>
@@ skipping 62 matching lines @@
   // If we return NO 30 times in a row, switch to being synchronous to avoid
   // burning CPU cycles on this callback.
   if (needs_display_) {
     did_not_draw_counter_ = 0;
   } else {
     did_not_draw_counter_ += 1;
     if (did_not_draw_counter_ == 30)
       [layer_ setAsynchronous:NO];
   }
 
-  // Add an instantaneous blip to the PendingSwapAck state to indicate
-  // that CoreAnimation asked if a frame is ready. A blip up to to 3 (usually
-  // from 2, indicating that a swap ack is pending) indicates that we
-  // requested a draw. A blip up to 1 (usually from 0, indicating there is no
-  // pending swap ack) indicates that we did not request a draw. This would
-  // be more natural to do with a tracing pseudo-thread
-  // http://crbug.com/366300
-  TRACE_COUNTER_ID1("browser", "PendingSwapAck", this, needs_display_ ? 3 : 1);
-  TRACE_COUNTER_ID1("browser", "PendingSwapAck", this,
-                    has_pending_frame_ ? 2 : 0);
+  if (needs_display_) {
+    // If there is a draw pending then increase the signal from 2 to 3, to
+    // indicate that we are in the state where there is a swap pending and
+    // CoreAnimation has been committed to draw it.
+    TRACE_COUNTER_ID1("browser", "PendingSwapAck", this, 3);
+  } else {
+    // If there is not a draw pending, then give an instantaneous blip up from
+    // 0 to 1, indicating that CoreAnimation was ready to draw a frame but we
+    // were not (or didn't have new content to draw).
+    TRACE_COUNTER_ID1("browser", "PendingSwapAck", this, 1);
+    TRACE_COUNTER_ID1("browser", "PendingSwapAck", this, 0);
+  }
 
   return needs_display_;
 }
 
 void IOSurfaceLayerHelper::DidDraw(bool success) {
   needs_display_ = false;
   AckPendingFrame(success);
 }
 
 void IOSurfaceLayerHelper::AckPendingFrame(bool success) {
@@ skipping 188 matching lines @@
   if (helper_)
     helper_->DidDraw(draw_succeeded);
 
   [super drawInCGLContext:glContext
               pixelFormat:pixelFormat
              forLayerTime:timeInterval
               displayTime:timeStamp];
 }
 
 @end