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

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 25366468f7d94cb79e7684661397e9aff288301f..f73e298a9f604ed7bd543e0b0deee9c8e5d8fdd9 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -17,6 +17,7 @@
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/layer_animation_controller.h"
 #include "cc/base/math_util.h"
+#include "cc/debug/devtools_instrumentation.h"
 #include "cc/debug/overdraw_metrics.h"
 #include "cc/debug/rendering_stats_instrumentation.h"
 #include "cc/input/top_controls_manager.h"
@@ -96,7 +97,8 @@ LayerTreeHost::LayerTreeHost(LayerTreeHostClient* client,
       has_transparent_background_(false),
       partial_texture_update_requests_(0),
       in_paint_layer_contents_(false),
-      total_frames_used_for_lcd_text_metrics_(0) {
+      total_frames_used_for_lcd_text_metrics_(0),
+      instrumentation_cookie_(0) {

[nduca, 2013/06/26 05:08:46]

do you still need the cookie init now?

   if (settings_.accelerated_animation_enabled)
     animation_registrar_ = AnimationRegistrar::Create();
   s_num_layer_tree_instances++;
@@ -946,6 +948,8 @@ bool LayerTreeHost::PaintLayerContents(
              it->render_surface()->draw_opacity_is_animating());
       need_more_updates |= PaintMasksForRenderSurface(*it, queue, stats_ptr);
     } else if (it.represents_itself()) {
+      devtools_instrumentation::ScopedLayerTreeTask
+          update_layer(devtools_instrumentation::kUpdateLayer, it->id(), id());
       DCHECK(!it->paint_properties().bounds.IsEmpty());
       it->Update(queue, &occlusion_tracker, stats_ptr);
       need_more_updates |= it->NeedMoreUpdates();