cc: Implement and use FilterOperations::MapRectReverse for mapping backdrop bounding box.

cc/output/filter_operations.h

 // Copyright 2013 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.
 
 #ifndef CC_OUTPUT_FILTER_OPERATIONS_H_
 #define CC_OUTPUT_FILTER_OPERATIONS_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 40 matching lines @@
 
   // Removes all filter operations.
   void Clear();
 
   bool IsEmpty() const;
 
   // Maps "forward" to determine which pixels in a destination rect are affected
   // by pixels in the source rect.
   gfx::Rect MapRect(const gfx::Rect& rect, const SkMatrix& matrix) const;
 
+  // Maps "backward" to determine which pixels in the source affect the pixels
+  // in the destination rect.
+  gfx::Rect MapRectReverse(const gfx::Rect& rect, const SkMatrix& matrix) const;
+
   void GetOutsets(int* top, int* right, int* bottom, int* left) const;
   bool HasFilterThatMovesPixels() const;
   bool HasFilterThatAffectsOpacity() const;
   bool HasReferenceFilter() const;
 
   size_t size() const {
     return operations_.size();
   }
 
   const std::vector<FilterOperation>& operations() const { return operations_; }
@@ skipping 17 matching lines @@
 
   void AsValueInto(base::trace_event::TracedValue* value) const;
 
  private:
   std::vector<FilterOperation> operations_;
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_FILTER_OPERATIONS_H_