Remove CompositeAndReadback from LayerTreeHost(Impl) and the Proxys.

cc/output/gl_renderer_unittest.cc

Index: cc/output/gl_renderer_unittest.cc
diff --git a/cc/output/gl_renderer_unittest.cc b/cc/output/gl_renderer_unittest.cc
index c5d729cd28659acc63c331626a67122758a35e61..253cf9843ff7ad380b2cb2729dc50a497f94430d 100644
--- a/cc/output/gl_renderer_unittest.cc
+++ b/cc/output/gl_renderer_unittest.cc
@@ -333,31 +333,6 @@ TEST_F(GLRendererWithDefaultHarnessTest,
   EXPECT_EQ(1u, output_surface_->num_sent_frames());
 }
 
-TEST_F(GLRendererWithDefaultHarnessTest,
-       FramebufferDiscardedAfterReadbackWhenNotVisible) {
-  gfx::Rect viewport_rect(1, 1);
-  renderer_->SetVisible(false);
-  EXPECT_TRUE(renderer_->IsBackbufferDiscarded());
-  EXPECT_EQ(1, renderer_client_.set_full_root_layer_damage_count());
-
-  AddRenderPass(&render_passes_in_draw_order_,
-                RenderPass::Id(1, 0),
-                viewport_rect,
-                gfx::Transform());
-
-  char pixels[4];
-  renderer_->DrawFrame(&render_passes_in_draw_order_,
-                       1.f,
-                       viewport_rect,
-                       viewport_rect,
-                       false);
-  EXPECT_FALSE(renderer_->IsBackbufferDiscarded());
-
-  renderer_->GetFramebufferPixels(pixels, gfx::Rect(0, 0, 1, 1));
-  EXPECT_TRUE(renderer_->IsBackbufferDiscarded());
-  EXPECT_EQ(2, renderer_client_.set_full_root_layer_damage_count());
-}
-
 TEST_F(GLRendererWithDefaultHarnessTest, ExternalStencil) {
   gfx::Rect viewport_rect(1, 1);
   EXPECT_FALSE(renderer_->stencil_enabled());