cc: Always check for completed raster tasks before scheduling more tasks.

cc/resources/pixel_buffer_raster_worker_pool.cc

 // Copyright 2013 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/resources/pixel_buffer_raster_worker_pool.h"
 
 #include "base/containers/stack_container.h"
 #include "base/debug/trace_event.h"
 #include "base/values.h"
 #include "cc/debug/traced_value.h"
@@ skipping 136 matching lines @@
 
   tasks_required_for_activation_.clear();
 
   // Build new pixel buffer task set.
   TaskMap new_pixel_buffer_tasks;
   for (RasterTaskVector::const_iterator it = raster_tasks().begin();
        it != raster_tasks().end(); ++it) {
     internal::RasterWorkerPoolTask* task = it->get();
     DCHECK(new_pixel_buffer_tasks.find(task) == new_pixel_buffer_tasks.end());
     DCHECK(!task->HasCompleted());
+    DCHECK(!task->WasCanceled());
 
     new_pixel_buffer_tasks[task] = pixel_buffer_tasks_[task];
     pixel_buffer_tasks_.erase(task);
 
     if (IsRasterTaskRequiredForActivation(task))
       tasks_required_for_activation_.insert(task);
   }
 
   // Transfer remaining pixel buffer tasks to |new_pixel_buffer_tasks|
   // and cancel all remaining inactive tasks.
@@ skipping 496 matching lines @@
 
   throttle_state->SetInteger("bytes_available_for_upload",
                              max_bytes_pending_upload_ - bytes_pending_upload_);
   throttle_state->SetInteger("bytes_pending_upload", bytes_pending_upload_);
   throttle_state->SetInteger("scheduled_raster_task_count",
                              scheduled_raster_task_count_);
   return throttle_state.PassAs<base::Value>();
 }
 
 }  // namespace cc