cc: Fix up code to work with concrete cc paint types

cc/trees/layer_tree_host_pixeltest_masks.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 <stddef.h>
 
 #include "build/build_config.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_image_layer.h"
 #include "cc/layers/picture_layer.h"
@@ skipping 85 matching lines @@
       gfx::Rect(100, 100), SK_ColorWHITE);
 
   gfx::Size mask_bounds(50, 50);
 
   scoped_refptr<PictureImageLayer> mask = PictureImageLayer::Create();
   mask->SetIsDrawable(true);
   mask->SetLayerMaskType(Layer::LayerMaskType::MULTI_TEXTURE_MASK);
   mask->SetBounds(mask_bounds);
 
   sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(200, 200);
-  PaintCanvas* canvas = surface->getCanvas();
+  SkCanvas* canvas = surface->getCanvas();
   canvas->scale(SkIntToScalar(4), SkIntToScalar(4));
   MaskContentLayerClient client(mask_bounds);
   scoped_refptr<DisplayItemList> mask_display_list =
       client.PaintContentsToDisplayList(
           ContentLayerClient::PAINTING_BEHAVIOR_NORMAL);
   mask_display_list->Raster(canvas, nullptr);
   mask->SetImage(surface->makeImageSnapshot());
 
   scoped_refptr<SolidColorLayer> green = CreateSolidColorLayerWithBorder(
       gfx::Rect(25, 25, 50, 50), kCSSGreen, 1, SK_ColorBLACK);
@@ skipping 218 matching lines @@
 
   RunPixelResourceTest(background,
                        base::FilePath(
                            FILE_PATH_LITERAL("mask_of_layer_with_blend.png")));
 }
 
 }  // namespace
 }  // namespace cc
 
 #endif  // !defined(OS_ANDROID)