Turn off computation of the interest rect in cc in synchronized paint mode.

cc/layers/picture_layer.cc

 // Copyright 2012 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/layers/picture_layer.h"
 
 #include "base/auto_reset.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_layer_impl.h"
 #include "cc/playback/display_list_recording_source.h"
@@ skipping 114 matching lines @@
   recording_source_->SetBackgroundColor(SafeOpaqueBackgroundColor());
   recording_source_->SetRequiresClear(!contents_opaque() &&
                                       !client_->FillsBoundsCompletely());
 
   TRACE_EVENT1("cc", "PictureLayer::Update",
                "source_frame_number",
                layer_tree_host()->source_frame_number());
   devtools_instrumentation::ScopedLayerTreeTask update_layer(
       devtools_instrumentation::kUpdateLayer, id(), layer_tree_host()->id());
 
-  // Calling paint in WebKit can sometimes cause invalidations, so save
+  // Calling paint in Blink can sometimes cause invalidations, so save
   // off the invalidation prior to calling update.
+  // TODO(chrishtr): Blink should no longer be invalidating during paint.

[enne (OOO), 2015/11/18 21:31:58]

This isn't a thing to fix in this patch, but similarly we have some code in
Layer::Update about paint properties where Blink tries to resize layers during
paint.  If we can ignore those things too, it'd be a great cleanup.

[chrishtr, 2015/11/18 22:33:11]

Ok I'll do that in a followup, nice.

+  // Try to remove this code.
   pending_invalidation_.Swap(&recording_invalidation_);
   pending_invalidation_.Clear();
 
+  // TODO(chrishtr): implement this for synchronized paint.
   if (layer_tree_host()->settings().record_full_layer) {
     // Workaround for http://crbug.com/235910 - to retain backwards compat
     // the full page content must always be provided in the picture layer.
     update_rect = gfx::Rect(layer_size);
   }
 
   // UpdateAndExpandInvalidation will give us an invalidation that covers
   // anything not explicitly recorded in this frame. We give this region
   // to the impl side so that it drops tiles that may not have a recording
   // for them.
@@ skipping 58 matching lines @@
 
 bool PictureLayer::HasDrawableContent() const {
   return client_ && Layer::HasDrawableContent();
 }
 
 void PictureLayer::RunMicroBenchmark(MicroBenchmark* benchmark) {
   benchmark->RunOnLayer(this);
 }
 
 }  // namespace cc