Clamps to invalidation region of a PictureLayer to the layer bounds to avoid adding unecessary bulk

cc/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/picture_layer.h"
 
 #include "cc/layer_tree_impl.h"
 #include "cc/picture_layer_impl.h"
 #include "ui/gfx/rect_conversions.h"
 
@@ skipping 33 matching lines @@
 }
 
 void PictureLayer::setLayerTreeHost(LayerTreeHost* host) {
   Layer::setLayerTreeHost(host);
   if (host)
       pile_.SetMinContentsScale(host->settings().minimumContentsScale);
 }
 
 void PictureLayer::setNeedsDisplayRect(const gfx::RectF& layer_rect) {
   gfx::Rect rect = gfx::ToEnclosedRect(layer_rect);
-  pending_invalidation_.Union(rect);
+  if (!rect.IsEmpty()) {

[danakj, 2013/01/09 00:31:57]

you could also rect.Intersect(gfx::Rect(contentBounds()) to do this on one line.

+    // Clamp invalidation to the layer bounds.
+    gfx::Rect clamped_rect = gfx::IntersectRects(
+        rect,
+        gfx::Rect(contentBounds()));
+    if (!clamped_rect.IsEmpty())
+      pending_invalidation_.Union(clamped_rect);

[danakj, 2013/01/09 00:31:57]

union with an empty rect is a no-op, so you probably don't need the if()?

+  }
   Layer::setNeedsDisplayRect(layer_rect);
 }
 
 void PictureLayer::update(ResourceUpdateQueue&, const OcclusionTracker*,
                     RenderingStats& stats) {
   if (pile_.size() == bounds() && pending_invalidation_.IsEmpty())
     return;
 
   pile_.Resize(bounds());
 
   // Calling paint in WebKit can sometimes cause invalidations, so save
   // off the invalidation prior to calling update.
   pile_invalidation_.Swap(pending_invalidation_);
   pending_invalidation_.Clear();
 
   pile_.Update(client_, pile_invalidation_, stats);
 }
 
 void PictureLayer::setIsMask(bool is_mask) {
   is_mask_ = is_mask;
 }
 
 }  // namespace cc