Update GatherPixelRefDevice to the new SkImage/SkPixelRef API

cc/playback/picture_pile_impl_unittest.cc

Index: cc/playback/picture_pile_impl_unittest.cc
diff --git a/cc/playback/picture_pile_impl_unittest.cc b/cc/playback/picture_pile_impl_unittest.cc
index f39f76c318715707e8c60a521b9847f6c9762674..e32ecbd66c9ad644d0e91057a0d0a2bafb32467b 100644
--- a/cc/playback/picture_pile_impl_unittest.cc
+++ b/cc/playback/picture_pile_impl_unittest.cc
@@ -167,9 +167,9 @@ TEST(PicturePileImplTest, PixelRefIteratorDiscardableRefsOneTile) {
       FakePicturePile::CreateFilledPile(tile_size, layer_bounds);
 
   SkBitmap discardable_bitmap[2][2];
-  CreateBitmap(gfx::Size(32, 32), "discardable", &discardable_bitmap[0][0]);
-  CreateBitmap(gfx::Size(32, 32), "discardable", &discardable_bitmap[0][1]);
-  CreateBitmap(gfx::Size(32, 32), "discardable", &discardable_bitmap[1][1]);
+  CreateDiscardableBitmap(gfx::Size(32, 32), &discardable_bitmap[0][0]);
+  CreateDiscardableBitmap(gfx::Size(32, 32), &discardable_bitmap[0][1]);
+  CreateDiscardableBitmap(gfx::Size(32, 32), &discardable_bitmap[1][1]);
 
   // Discardable pixel refs are found in the following cells:
   // |---|---|
@@ -530,7 +530,7 @@ TEST(PicturePileImplTest, PixelRefIteratorBorders) {
   SkBitmap discardable_bitmap[arraysize(bitmap_rects)];
 
   for (size_t i = 0; i < arraysize(bitmap_rects); ++i) {
-    CreateBitmap(bitmap_rects[i].size(), "discardable", &discardable_bitmap[i]);
+    CreateDiscardableBitmap(bitmap_rects[i].size(), &discardable_bitmap[i]);
     recording_source->add_draw_bitmap(discardable_bitmap[i],
                                       bitmap_rects[i].origin());
   }