Make gfx::Rect class operations consistently mutate the class they are called on.

content/common/gpu/image_transport_surface.cc

Index: content/common/gpu/image_transport_surface.cc
diff --git a/content/common/gpu/image_transport_surface.cc b/content/common/gpu/image_transport_surface.cc
index 1b1428b02f0a82d901616908265aa87c8b2394ca..911b7278a9ea469be1eeea85d0d51cc659bb5b91 100644
--- a/content/common/gpu/image_transport_surface.cc
+++ b/content/common/gpu/image_transport_surface.cc
@@ -30,7 +30,8 @@ void ImageTransportSurface::GetRegionsToCopy(
     const gfx::Rect& previous_damage_rect,
     const gfx::Rect& new_damage_rect,
     std::vector<gfx::Rect>* regions) {
-  gfx::Rect intersection = previous_damage_rect.Intersect(new_damage_rect);
+  gfx::Rect intersection = previous_damage_rect;
+  intersection.Intersect(new_damage_rect);
 
   if (intersection.IsEmpty()) {
     regions->push_back(previous_damage_rect);