Skip geometry mapping when source and destination spaces are equal

third_party/WebKit/Source/platform/graphics/paint/GeometryMapper.cpp

 // Copyright 2016 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 "platform/graphics/paint/GeometryMapper.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/LayoutRect.h"
 
 namespace blink {
 
 FloatRect GeometryMapper::mapToVisualRectInDestinationSpace(
     const FloatRect& rect,
     const PropertyTreeState& sourceState,
     const PropertyTreeState& destinationState,
     bool& success) {
+  if (sourceState == destinationState) {
+    success = true;
+    return rect;
+  }
   FloatRect result = localToVisualRectInAncestorSpace(
       rect, sourceState, destinationState, success);
   if (success)
     return result;
   return slowMapToVisualRectInDestinationSpace(rect, sourceState,
                                                destinationState, success);
 }
 
 FloatRect GeometryMapper::mapRectToDestinationSpace(
     const FloatRect& rect,
     const PropertyTreeState& sourceState,
     const PropertyTreeState& destinationState,
     bool& success) {
+  if (sourceState == destinationState) {
+    success = true;
+    return rect;
+  }
   FloatRect result =
       localToAncestorRect(rect, sourceState, destinationState, success);
   if (success)
     return result;
   return slowMapRectToDestinationSpace(rect, sourceState, destinationState,
                                        success);
 }
 
 FloatRect GeometryMapper::slowMapToVisualRectInDestinationSpace(
     const FloatRect& rect,
@@ skipping 264 matching lines @@
 
   // Walk up until we find the ancestor.
   while (a != b) {
     a = a->parent();
     b = b->parent();
   }
   return a;
 }
 
 }  // namespace blink