Fix ImageUploadTaskImpl with null dependencies.

cc/tiles/gpu_image_decode_controller.cc

 // Copyright 2016 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/tiles/gpu_image_decode_controller.h"
 
 #include "base/memory/discardable_memory_allocator.h"
 #include "base/memory/ptr_util.h"
 #include "base/numerics/safe_math.h"
 #include "base/strings/stringprintf.h"
@@ skipping 92 matching lines @@
   ImageUploadTaskImpl(GpuImageDecodeController* controller,
                       const DrawImage& draw_image,
                       scoped_refptr<TileTask> decode_dependency,
                       uint64_t source_prepare_tiles_id)
       : TileTask(false),
         controller_(controller),
         image_(draw_image),
         image_ref_(draw_image.image()),
         source_prepare_tiles_id_(source_prepare_tiles_id) {
     DCHECK(!SkipImage(draw_image));
-    dependencies_.push_back(std::move(decode_dependency));
+    if (decode_dependency) {

[vmpstr, 2016/04/20 22:26:44]

nit: no braces

Also, the unittest makes it clear, but can you add a short comment to explain
when this might be null?

[ericrk, 2016/04/20 22:34:45]

Done.

+      dependencies_.push_back(std::move(decode_dependency));
+    }
   }
 
   // Override from Task:
   void RunOnWorkerThread() override {
     TRACE_EVENT2("cc", "ImageUploadTaskImpl::RunOnWorkerThread", "mode", "gpu",
                  "source_prepare_tiles_id", source_prepare_tiles_id_);
     controller_->UploadImage(image_);
   }
 
   void ScheduleOnOriginThread(RasterBufferProvider* provider) override {}
@@ skipping 613 matching lines @@
 }
 
 SkImageInfo GpuImageDecodeController::CreateImageInfoForDrawImage(
     const DrawImage& draw_image) const {
   return SkImageInfo::Make(
       draw_image.image()->width(), draw_image.image()->height(),
       ResourceFormatToClosestSkColorType(format_), kPremul_SkAlphaType);
 }
 
 }  // namespace cc