cc::SharedQuadState: drop CopyFrom and add copy constructor

cc/quads/shared_quad_state.h

Index: cc/quads/shared_quad_state.h
diff --git a/cc/quads/shared_quad_state.h b/cc/quads/shared_quad_state.h
index 35da669c30910c9f9db7d2d0bac9b5a3c3c57895..75f603fe6a6c24fb3ef4e440abc00ebf51a7c195 100644
--- a/cc/quads/shared_quad_state.h
+++ b/cc/quads/shared_quad_state.h
@@ -29,10 +29,9 @@ namespace cc {
 class CC_EXPORT SharedQuadState {
  public:
   SharedQuadState();
+  SharedQuadState(const SharedQuadState& other);
   ~SharedQuadState();
 
-  void CopyFrom(const SharedQuadState* other);
-
   void SetAll(const gfx::Transform& quad_to_target_transform,
               const gfx::Size& layer_bounds,
               const gfx::Rect& visible_layer_rect,