cc::SharedQuadState: drop CopyFrom and add copy constructor

cc/quads/shared_quad_state.cc

Index: cc/quads/shared_quad_state.cc
diff --git a/cc/quads/shared_quad_state.cc b/cc/quads/shared_quad_state.cc
index aa630c52f3959dc80b6e6f491ed2c6d6919386e8..cd75f947396c4f99271c47bbcc25aa0bad0bd4f8 100644
--- a/cc/quads/shared_quad_state.cc
+++ b/cc/quads/shared_quad_state.cc
@@ -19,16 +19,14 @@ SharedQuadState::SharedQuadState()
       sorting_context_id(0) {
 }
 
+SharedQuadState::SharedQuadState(const SharedQuadState& other) = default;
+
 SharedQuadState::~SharedQuadState() {
   TRACE_EVENT_OBJECT_DELETED_WITH_ID(
       TRACE_DISABLED_BY_DEFAULT("cc.debug.quads"),
       "cc::SharedQuadState", this);
 }
 
-void SharedQuadState::CopyFrom(const SharedQuadState* other) {
-  *this = *other;
-}
-
 void SharedQuadState::SetAll(const gfx::Transform& quad_to_target_transform,
                              const gfx::Size& quad_layer_bounds,
                              const gfx::Rect& visible_quad_layer_rect,