cc: Move SkShader construction to a single spot in PaintShader

cc/paint/discardable_image_map_unittest.cc

 // Copyright 2015 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 "cc/paint/discardable_image_map.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 582 matching lines @@
   // transforms, so we can't let the scale drop all the way to 0.
   static constexpr float kMinScale = 0.1f;
 
   for (int y = 0; y < 4; ++y) {
     for (int x = 0; x < 4; ++x) {
       if ((x + y) & 1) {
         discardable_image[y][x] = CreateDiscardableImage(gfx::Size(500, 500));
         SkMatrix scale = SkMatrix::MakeScale(std::max(x * 0.5f, kMinScale),
                                              std::max(y * 0.5f, kMinScale));
         PaintFlags flags;
-        flags.setShader(discardable_image[y][x]->makeShader(
-            SkShader::kClamp_TileMode, SkShader::kClamp_TileMode, &scale));
+        flags.setShader(base::MakeUnique<PaintShader>(
+            discardable_image[y][x], SkShader::kClamp_TileMode,
+            SkShader::kClamp_TileMode, &scale));
         content_layer_client.add_draw_rect(
             gfx::Rect(x * 512 + 6, y * 512 + 6, 500, 500), flags);
       }
     }
   }
 
   scoped_refptr<DisplayItemList> display_list =
       content_layer_client.PaintContentsToDisplayList(
           ContentLayerClient::PAINTING_BEHAVIOR_NORMAL);
   display_list->GenerateDiscardableImagesMetadata();
@@ skipping 94 matching lines @@
   EXPECT_TRUE(discardable_image == images[0].paint_image());
 
   images.clear();
   image_map_.GetDiscardableImagesInRect(gfx::Rect(105, 105, 5, 95), 1.f,
                                         target_color_space, &images);
   EXPECT_EQ(1u, images.size());
   EXPECT_TRUE(discardable_image2 == images[0].paint_image());
 }
 
 }  // namespace cc