CC: Force push properties for all layers when tracing is started

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 197 matching lines @@
 }
 
 void LayerTreeHost::SetLayerTreeHostClientReady() {
   proxy_->SetLayerTreeHostClientReady();
 }
 
 static void LayerTreeHostOnOutputSurfaceCreatedCallback(Layer* layer) {
   layer->OnOutputSurfaceCreated();
 }
 
+static void LayerTreeHostDidBeginTracingCallback(Layer* layer) {
+  layer->DidBeginTracing();
+}
+
 void LayerTreeHost::DeleteContentsTexturesOnImplThread(
     ResourceProvider* resource_provider) {
   DCHECK(proxy_->IsImplThread());
   if (contents_texture_manager_)
     contents_texture_manager_->ClearAllMemory(resource_provider);
 }
 
 void LayerTreeHost::WillBeginMainFrame() {
   devtools_instrumentation::WillBeginMainThreadFrame(id(),
                                                      source_frame_number());
@@ skipping 63 matching lines @@
 
   LayerTreeImpl* sync_tree = host_impl->sync_tree();
 
   if (next_commit_forces_redraw_) {
     sync_tree->ForceRedrawNextActivation();
     next_commit_forces_redraw_ = false;
   }
 
   sync_tree->set_source_frame_number(source_frame_number());
 
+  bool is_new_trace;
+  TRACE_EVENT_IS_NEW_TRACE(&is_new_trace);
+  if (is_new_trace) {
+    // We're about to start tracing snaphsots of layer tree, so force
+    // push properties for all layers to propagate LayerDebugInfo to

[danakj, 2015/03/06 18:50:12]

I see, LayerDebugInfo is a type, up in ui/compositor/ but that only is relevant
for the ui compositor, not for the renderer, so referring to it here is a
layering violation. Can you make this comment more general so it's accurate for
the renderer too?

+    // the impl side.
+    bool will_snapshot_layer_tree;
+    TRACE_EVENT_CATEGORY_GROUP_ENABLED(
+        TRACE_DISABLED_BY_DEFAULT("cc.debug") "," TRACE_DISABLED_BY_DEFAULT(

[danakj, 2015/03/06 18:50:12]

I don't like that these magic categories appear here and just kinda "know" what
will get traced later. How can we ensure this isn't going to get out of sync at
some point and cause bugs?

(I don't even see the devtools.timeline.layers mentioned here:
https://code.google.com/p/chromium/codesearch#chromium/src/cc/layers/layer_im...)

+            "devtools.timeline.layers"),
+        &will_snapshot_layer_tree);
+    if (will_snapshot_layer_tree) {
+      LayerTreeHostCommon::CallFunctionForSubtree(
+          root_layer(), base::Bind(LayerTreeHostDidBeginTracingCallback));

[danakj, 2015/03/06 18:50:12]

This will need a rebase.

+    }
+  }
+
   if (needs_full_tree_sync_) {
     sync_tree->SetRootLayer(TreeSynchronizer::SynchronizeTrees(
         root_layer(), sync_tree->DetachLayerTree(), sync_tree));
   }
   sync_tree->set_needs_full_tree_sync(needs_full_tree_sync_);
   needs_full_tree_sync_ = false;
 
   if (hud_layer_.get()) {
     LayerImpl* hud_impl = LayerTreeHostCommon::FindLayerInSubtree(
         sync_tree->root_layer(), hud_layer_->id());
@@ skipping 1016 matching lines @@
     bool children_need_begin_frames) const {
   proxy_->SetChildrenNeedBeginFrames(children_need_begin_frames);
 }
 
 void LayerTreeHost::SendBeginFramesToChildren(
     const BeginFrameArgs& args) const {
   client_->SendBeginFramesToChildren(args);
 }
 
 }  // namespace cc