cc::SharedQuadState: drop CopyFrom and add copy constructor

cc/quads/draw_quad_unittest.cc

Index: cc/quads/draw_quad_unittest.cc
diff --git a/cc/quads/draw_quad_unittest.cc b/cc/quads/draw_quad_unittest.cc
index 4172d940873536c62139a0c2500ed36bb0b4d0a4..8045d8c00126e6df8ea860f0f342805c068c7dd6 100644
--- a/cc/quads/draw_quad_unittest.cc
+++ b/cc/quads/draw_quad_unittest.cc
@@ -46,8 +46,7 @@ TEST(DrawQuadTest, CopySharedQuadState) {
   state->SetAll(quad_transform, layer_bounds, visible_layer_rect, clip_rect,
                 is_clipped, opacity, blend_mode, sorting_context_id);
 
-  std::unique_ptr<SharedQuadState> copy(new SharedQuadState);
-  copy->CopyFrom(state.get());
+  std::unique_ptr<SharedQuadState> copy(new SharedQuadState(*state));
   EXPECT_EQ(quad_transform, copy->quad_to_target_transform);
   EXPECT_EQ(visible_layer_rect, copy->visible_quad_layer_rect);
   EXPECT_EQ(opacity, copy->opacity);
@@ -88,7 +87,7 @@ void CompareDrawQuad(DrawQuad* quad,
   SharedQuadState* shared_state(CreateSharedQuadState(render_pass.get())); \
   SharedQuadState* copy_shared_state =                                     \
       render_pass->CreateAndAppendSharedQuadState();                       \
-  copy_shared_state->CopyFrom(shared_state);
+  *copy_shared_state = *shared_state;
 
 #define QUAD_DATA                              \
   gfx::Rect quad_rect(30, 40, 50, 60);         \