Use the solid color detection to create solid layers

cc/trees/layer_tree_host_pixeltest_readback.cc

 // Copyright 2013 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.
 
 #include "build/build_config.h"
 #include "cc/layers/solid_color_layer.h"
 #include "cc/layers/texture_layer.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/output/copy_output_result.h"
 #include "cc/test/fake_picture_layer.h"
@@ skipping 913 matching lines @@
     // Cause the device scale factor to be inherited by contents scales.
     settings->layer_transforms_should_scale_layer_contents = true;
   }
 
   virtual void SetupTree() OVERRIDE {
     layer_tree_host()->SetDeviceScaleFactor(device_scale_factor_);
     LayerTreePixelTest::SetupTree();
   }
 
   virtual void DrawLayersOnThread(LayerTreeHostImpl* host_impl) OVERRIDE {
-    LayerImpl* root_impl = host_impl->active_tree()->root_layer();
-
-    FakePictureLayerImpl* background_impl =
-        static_cast<FakePictureLayerImpl*>(root_impl->children()[0]);
     EXPECT_EQ(device_scale_factor_,
-              background_impl->HighResTiling()->contents_scale());
-
-    FakePictureLayerImpl* green_impl =
-        static_cast<FakePictureLayerImpl*>(background_impl->children()[0]);
-    EXPECT_EQ(device_scale_factor_,
-              green_impl->HighResTiling()->contents_scale());
-
-    FakePictureLayerImpl* blue_impl =
-        static_cast<FakePictureLayerImpl*>(green_impl->children()[0]);
-    EXPECT_EQ(device_scale_factor_,
-              blue_impl->HighResTiling()->contents_scale());
+              host_impl->active_tree()->device_scale_factor());
   }
 
   float device_scale_factor_;
   SolidColorContentLayerClient white_client_;
   SolidColorContentLayerClient green_client_;
   SolidColorContentLayerClient blue_client_;
 };
 
 TEST_F(LayerTreeHostReadbackDeviceScalePixelTest,
        ReadbackSubrect_Software) {
@@ skipping 134 matching lines @@
                                  background,
                                  green.get(),
                                  base::FilePath(FILE_PATH_LITERAL(
                                      "green_with_blue_corner.png")));
 }
 
 }  // namespace
 }  // namespace cc
 
 #endif  // OS_ANDROID