cc: Remove the opaque rect return-parameter from ContentLayerClient.

cc/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 component("cc") {
   sources = [
     "animation/animation.cc",
     "animation/animation.h",
     "animation/animation_curve.cc",
     "animation/animation_curve.h",
@@ skipping 645 matching lines @@
     "base/float_quad_unittest.cc",
     "base/math_util_unittest.cc",
     "base/region_unittest.cc",
     "base/rolling_time_delta_history_unittest.cc",
     "base/scoped_ptr_vector_unittest.cc",
     "base/simple_enclosed_region_unittest.cc",
     "base/tiling_data_unittest.cc",
     "base/util_unittest.cc",
     "debug/micro_benchmark_controller_unittest.cc",
     "input/top_controls_manager_unittest.cc",
-    "layers/content_layer_unittest.cc",
     "layers/contents_scaling_layer_unittest.cc",
     "layers/delegated_frame_provider_unittest.cc",
     "layers/delegated_frame_resource_collection_unittest.cc",
     "layers/delegated_renderer_layer_impl_unittest.cc",
     "layers/delegated_renderer_layer_unittest.cc",
     "layers/heads_up_display_unittest.cc",
     "layers/heads_up_display_layer_impl_unittest.cc",
     "layers/io_surface_layer_impl_unittest.cc",
     "layers/layer_impl_unittest.cc",
     "layers/layer_iterator_unittest.cc",
@@ skipping 134 matching lines @@
     "//gpu/command_buffer/common:gles2_utils",
     "//media",
     "//skia",
     "//testing/gmock",
     "//testing/gtest",
     "//testing/perf",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
 }