cc: Allow the main thread to cancel commits

cc/layers/layer.cc

 // Copyright 2010 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/layer.h"
 
 #include <algorithm>
 
 #include "base/location.h"
 #include "base/metrics/histogram.h"
@@ skipping 97 matching lines @@
       reset_raster_scale_to_unknown();
   }
 
   if (host && layer_animation_controller_->has_any_animation())
     host->SetNeedsCommit();
   if (host &&
       (!filters_.IsEmpty() || !background_filters_.IsEmpty() || filter_))
     layer_tree_host_->set_needs_filter_context();
 }
 
+void Layer::SetNeedsUpdate() {
+  if (layer_tree_host_)
+    layer_tree_host_->SetNeedsUpdateLayers();
+}
+
 void Layer::SetNeedsCommit() {
   if (ignore_set_needs_commit_)
     return;
   if (layer_tree_host_)
     layer_tree_host_->SetNeedsCommit();
 }
 
 void Layer::SetNeedsFullTreeSync() {
   if (layer_tree_host_)
     layer_tree_host_->SetNeedsFullTreeSync();
@@ skipping 382 matching lines @@
 void Layer::SetScrollOffset(gfx::Vector2d scroll_offset) {
   DCHECK(IsPropertyChangeAllowed());
   if (scroll_offset_ == scroll_offset)
     return;
   scroll_offset_ = scroll_offset;
   SetNeedsCommit();
 }
 
 void Layer::SetScrollOffsetFromImplSide(gfx::Vector2d scroll_offset) {
   DCHECK(IsPropertyChangeAllowed());
+  // This function only gets called during a begin frame, so there
+  // is no need to call SetNeedsUpdate here.
   DCHECK(layer_tree_host_ && layer_tree_host_->CommitRequested());
   if (scroll_offset_ == scroll_offset)
     return;
   scroll_offset_ = scroll_offset;
   if (!did_scroll_callback_.is_null())
     did_scroll_callback_.Run();
   // Note: didScroll() could potentially change the layer structure.
   //       "this" may have been destroyed during the process.
 }
 
@@ skipping 83 matching lines @@
     return;
 
   hide_layer_and_subtree_ = hide;
   SetNeedsCommit();
 }
 
 void Layer::SetNeedsDisplayRect(const gfx::RectF& dirty_rect) {
   update_rect_.Union(dirty_rect);
   needs_display_ = true;
 
-  // Simply mark the contents as dirty. For non-root layers, the call to
-  // SetNeedsCommit will schedule a fresh compositing pass.
-  // For the root layer, SetNeedsCommit has no effect.
   if (DrawsContent() && !update_rect_.IsEmpty())
-    SetNeedsCommit();
+    SetNeedsUpdate();
 }
 
 bool Layer::DescendantIsFixedToContainerLayer() const {
   for (size_t i = 0; i < children_.size(); ++i) {
     if (children_[i]->position_constraint_.is_fixed_position() ||
         children_[i]->DescendantIsFixedToContainerLayer())
       return true;
   }
   return false;
 }
@@ skipping 259 matching lines @@
 
 RenderingStatsInstrumentation* Layer::rendering_stats_instrumentation() const {
   return layer_tree_host_->rendering_stats_instrumentation();
 }
 
 bool Layer::SupportsLCDText() const {
   return false;
 }
 
 }  // namespace cc