Add LayerTreeHostClient::{will,did}UpdateLayer, report layer updates to DevTools

cc/debug/devtools_instrumentation.h

 // 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.
 
 #ifndef CC_DEBUG_DEVTOOLS_INSTRUMENTATION_H_
 #define CC_DEBUG_DEVTOOLS_INSTRUMENTATION_H_
 
 #include "base/debug/trace_event.h"
 
 namespace cc {
 namespace devtools_instrumentation {
 
 namespace internal {
 const char kCategory[] = "cc,devtools";
 const char kLayerId[] = "layerId";
+const char kLayerTreeId[] = "layerTreeId";
 }
 
 const char kPaintLayer[] = "PaintLayer";
 const char kRasterTask[] = "RasterTask";
 const char kImageDecodeTask[] = "ImageDecodeTask";
 const char kPaintSetup[] = "PaintSetup";
+const char kUpdateLayer[] = "UpdateLayer";
 
 class ScopedLayerTask {
  public:
-  explicit ScopedLayerTask(const char* event_name, int layer_id)
+  ScopedLayerTask(const char* event_name, int layer_id)
     : event_name_(event_name) {
     TRACE_EVENT_BEGIN1(internal::kCategory, event_name_,
         internal::kLayerId, layer_id);
   }
   ~ScopedLayerTask() {
     TRACE_EVENT_END0(internal::kCategory, event_name_);
   }
  private:
   const char* event_name_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedLayerTask);
+};
+
+class ScopedLayerTreeTask {
+ public:
+  ScopedLayerTreeTask(const char* event_name,
+                      int layer_id,
+                      uint64 tree_id)
+    : event_name_(event_name) {
+    TRACE_EVENT_BEGIN2(internal::kCategory, event_name_,
+        internal::kLayerId, layer_id, internal::kLayerTreeId, tree_id);
+  }
+  ~ScopedLayerTreeTask() {
+    TRACE_EVENT_END0(internal::kCategory, event_name_);
+  }
+ private:
+  const char* event_name_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedLayerTreeTask);
 };
 
 struct ScopedLayerObjectTracker
     : public base::debug::TraceScopedTrackableObject<int> {
   explicit ScopedLayerObjectTracker(int layer_id)
       : base::debug::TraceScopedTrackableObject<int>(
             internal::kCategory,
             internal::kLayerId,
             layer_id) {
   }
 
+ private:
   DISALLOW_COPY_AND_ASSIGN(ScopedLayerObjectTracker);
 };
 
 }  // namespace devtools_instrumentation
 }  // namespace cc
 
 #endif  // CC_DEBUG_DEVTOOLS_INSTRUMENTATION_H_