Add trace event for addition/removal of GPU rasterization trigger

cc/trees/layer_tree_host.cc

 // Copyright 2011 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 "cc/trees/layer_tree_host.h"
 
 #include <algorithm>
 #include <stack>
 #include <string>
 
@@ skipping 601 matching lines @@
   if (settings_.gpu_rasterization_forced) {
     return true;
   } else if (settings_.gpu_rasterization_enabled) {
     return has_gpu_rasterization_trigger_ &&
            content_is_suitable_for_gpu_rasterization_;
   } else {
     return false;
   }
 }
 
+void LayerTreeHost::SetHasGpuRasterizationTrigger(bool has_trigger) {
+  if (has_trigger == has_gpu_rasterization_trigger_)
+    return;
+
+  has_gpu_rasterization_trigger_ = has_trigger;
+  if (has_gpu_rasterization_trigger_) {
+    TRACE_EVENT_INSTANT0(

[ernstm, 2014/06/02 21:34:48]

Could you issue a TRACE_EVENT_INSTANT1 with name
"LayerTreeHost::SetHasGpuRasterizationTrigger" and a boolean data item
"has_trigger"? That would make it easier to process these events in telemetry.

[ajuma, 2014/06/03 14:47:11]

Done.

+        "cc",
+        "LayerTreeHost::SetHasGpuRasterizationTrigger trigger added",
+        TRACE_EVENT_SCOPE_THREAD);
+  } else {
+    TRACE_EVENT_INSTANT0(
+        "cc",
+        "LayerTreeHost::SetHasGpuRasterizationTrigger trigger removed",
+        TRACE_EVENT_SCOPE_THREAD);
+  }
+}
+
 void LayerTreeHost::SetViewportSize(const gfx::Size& device_viewport_size) {
   if (device_viewport_size == device_viewport_size_)
     return;
 
   device_viewport_size_ = device_viewport_size;
 
   SetNeedsCommit();
 }
 
 void LayerTreeHost::SetOverdrawBottomHeight(float overdraw_bottom_height) {
@@ skipping 648 matching lines @@
   swap_promise_list_.push_back(swap_promise.Pass());
 }
 
 void LayerTreeHost::BreakSwapPromises(SwapPromise::DidNotSwapReason reason) {
   for (size_t i = 0; i < swap_promise_list_.size(); i++)
     swap_promise_list_[i]->DidNotSwap(reason);
   swap_promise_list_.clear();
 }
 
 }  // namespace cc