Add better support for RGBA_4444 textures.

cc/raster/tile_task_worker_pool.cc

Index: cc/raster/tile_task_worker_pool.cc
diff --git a/cc/raster/tile_task_worker_pool.cc b/cc/raster/tile_task_worker_pool.cc
index f9862fbab1a203c56774038e5a86f0718787630f..6b1eb1e3eeb82d0f0c0309d3c6af111a9bb364b5 100644
--- a/cc/raster/tile_task_worker_pool.cc
+++ b/cc/raster/tile_task_worker_pool.cc
@@ -225,18 +225,22 @@ void TileTaskWorkerPool::PlaybackToMemory(void* memory,
   skia::RefPtr<SkCanvas> canvas = skia::SharePtr(surface->getCanvas());
   canvas->setDrawFilter(image_filter.get());
   raster_source->PlaybackToCanvas(canvas.get(), canvas_bitmap_rect,
-                                  canvas_playback_rect, scale);
-
-  SkImageInfo dst_info =
-      SkImageInfo::Make(info.width(), info.height(), buffer_color_type,
-                        info.alphaType(), info.profileType());
-  // TODO(kaanb): The GL pipeline assumes a 4-byte alignment for the
-  // bitmap data. There will be no need to call SkAlign4 once crbug.com/293728
-  // is fixed.
-  const size_t dst_row_bytes = SkAlign4(dst_info.minRowBytes());
-  DCHECK_EQ(0u, dst_row_bytes % 4);
-  bool success = canvas->readPixels(dst_info, memory, dst_row_bytes, 0, 0);
-  DCHECK_EQ(true, success);
+                                  canvas_bitmap_rect, scale);

[reveman, 2015/08/10 23:19:01]

Note: this change is needed to make the code below work with partial updates. It
basically disables partial updates when we have to convert pixels. I think we
can improve this but I prefer to keep it simple until texture compression
patches have landed. 

[danakj, 2015/08/10 23:35:54]

Can you file a bug and point to it in a TODO saying that this should be
canvas_playback_rect to get partial updates and why it's not etc?

[reveman, 2015/08/10 23:49:41]

Added TODO.

+
+  {
+    TRACE_EVENT0("cc", "TileTaskWorkerPool::PlaybackToMemory::ConvertPixels");
+
+    SkImageInfo dst_info =
+        SkImageInfo::Make(info.width(), info.height(), buffer_color_type,
+                          info.alphaType(), info.profileType());
+    // TODO(kaanb): The GL pipeline assumes a 4-byte alignment for the
+    // bitmap data. There will be no need to call SkAlign4 once crbug.com/293728
+    // is fixed.
+    const size_t dst_row_bytes = SkAlign4(dst_info.minRowBytes());
+    DCHECK_EQ(0u, dst_row_bytes % 4);
+    bool success = canvas->readPixels(dst_info, memory, dst_row_bytes, 0, 0);
+    DCHECK_EQ(true, success);
+  }
 }
 
 }  // namespace cc