cc: Simplify task and its derived classes.

cc/raster/zero_copy_tile_task_worker_pool.h

Index: cc/raster/zero_copy_tile_task_worker_pool.h
diff --git a/cc/raster/zero_copy_tile_task_worker_pool.h b/cc/raster/zero_copy_tile_task_worker_pool.h
index bc558d762ce9e103022ad7a11ba08dccecce1e06..eb3fe7a7b41fe93a03fbaa2a5c20f489a3e208d1 100644
--- a/cc/raster/zero_copy_tile_task_worker_pool.h
+++ b/cc/raster/zero_copy_tile_task_worker_pool.h
@@ -24,7 +24,7 @@ class ResourceProvider;
 
 class CC_EXPORT ZeroCopyTileTaskWorkerPool : public TileTaskWorkerPool,
                                              public TileTaskRunner,
-                                             public TileTaskClient {
+                                             public DependencyTaskClient {
  public:
   ~ZeroCopyTileTaskWorkerPool() override;
 
@@ -44,7 +44,7 @@ class CC_EXPORT ZeroCopyTileTaskWorkerPool : public TileTaskWorkerPool,
   ResourceFormat GetResourceFormat(bool must_support_alpha) const override;
   bool GetResourceRequiresSwizzle(bool must_support_alpha) const override;
 
-  // Overridden from TileTaskClient:
+  // Overridden from DependencyTaskClient:
   scoped_ptr<RasterBuffer> AcquireBufferForRaster(
       const Resource* resource,
       uint64_t resource_content_id,
@@ -67,7 +67,7 @@ class CC_EXPORT ZeroCopyTileTaskWorkerPool : public TileTaskWorkerPool,
 
   ResourceFormat preferred_tile_format_;
 
-  Task::Vector completed_tasks_;
+  DependencyTask::Vector completed_tasks_;
 
   DISALLOW_COPY_AND_ASSIGN(ZeroCopyTileTaskWorkerPool);
 };