cc: Simplify task and its derived classes.

cc/raster/one_copy_tile_task_worker_pool.cc

Index: cc/raster/one_copy_tile_task_worker_pool.cc
diff --git a/cc/raster/one_copy_tile_task_worker_pool.cc b/cc/raster/one_copy_tile_task_worker_pool.cc
index 79429ad36a2cf8001302f2cb032e4e4a73ad24f9..032046516d36d29829767fb8f078e8411e80ddc0 100644
--- a/cc/raster/one_copy_tile_task_worker_pool.cc
+++ b/cc/raster/one_copy_tile_task_worker_pool.cc
@@ -19,7 +19,6 @@
 #include "cc/base/container_util.h"
 #include "cc/base/math_util.h"
 #include "cc/debug/traced_value.h"
-#include "cc/raster/raster_buffer.h"
 #include "cc/resources/platform_color.h"
 #include "cc/resources/resource_format.h"
 #include "cc/resources/resource_util.h"
@@ -256,7 +255,7 @@ void OneCopyTileTaskWorkerPool::Shutdown() {
 void OneCopyTileTaskWorkerPool::ScheduleTasks(TaskGraph* graph) {
   TRACE_EVENT0("cc", "OneCopyTileTaskWorkerPool::ScheduleTasks");
 
-  ScheduleTasksOnOriginThread(this, graph);
+  ScheduleTasksOnOriginThread(graph);
 
   // Barrier to sync any new resources to the worker context.
   resource_provider_->output_surface()
@@ -275,10 +274,10 @@ void OneCopyTileTaskWorkerPool::CheckForCompletedTasks() {
 
   for (Task::Vector::const_iterator it = completed_tasks_.begin();
        it != completed_tasks_.end(); ++it) {
-    TileTask* task = static_cast<TileTask*>(it->get());
+    Task* task = it->get();
 
     task->WillComplete();
-    task->CompleteOnOriginThread(this);
+    task->CompleteOnOriginThread();
     task->DidComplete();
   }
   completed_tasks_.clear();