Fix for 424682: Draw correct repaint regions instead of a conservative bounding box

cc/layers/picture_layer_impl.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_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <set>
@@ skipping 587 matching lines @@
   // To avoid an edge case after lost context where the tree is up to date but
   // the tilings have not been managed, request an update draw properties
   // to force tilings to get managed.
   layer_tree_impl()->set_needs_update_draw_properties();
 }
 
 skia::RefPtr<SkPicture> PictureLayerImpl::GetPicture() {
   return raster_source_->GetFlattenedPicture();
 }
 
+Region PictureLayerImpl::GetInvalidationRegion() {
+  // |invalidation_| gives the invalidation contained in the source frame, but
+  // is not cleared after drawing from the layer. However, update_rect() is
+  // cleared once the invalidation is drawn, which is useful for debugging
+  // visualizations. This method intersects the two to give a more exact
+  // representation of what was invalidated that is cleared after drawing.
+  return IntersectRegions(invalidation_, update_rect());
+}
+
 scoped_refptr<Tile> PictureLayerImpl::CreateTile(
     float contents_scale,
     const gfx::Rect& content_rect) {
   int flags = 0;
 
   // We don't handle solid color masks, so we shouldn't bother analyzing those.
   // Otherwise, always analyze to maximize memory savings.
   if (!is_mask_)
     flags = Tile::USE_PICTURE_ANALYSIS;
 
@@ skipping 601 matching lines @@
 
 bool PictureLayerImpl::IsOnActiveOrPendingTree() const {
   return !layer_tree_impl()->IsRecycleTree();
 }
 
 bool PictureLayerImpl::HasValidTilePriorities() const {
   return IsOnActiveOrPendingTree() && IsDrawnRenderSurfaceLayerListMember();
 }
 
 }  // namespace cc