cc: Remove unused kOnDemandRasterTaskPriority.

BUG=
TBR=vmpstr@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/597443002

Cr-Commit-Position: refs/heads/master@{#296127}

cc/resources/raster_worker_pool.cc

@@ -88,9 +88,6 @@ class RasterFinishedTaskImpl : public RasterizerTask {
 
 }  // namespace
 
-// This allows an external rasterize on-demand system to run raster tasks
-// with highest priority using the same task graph runner instance.
-unsigned RasterWorkerPool::kOnDemandRasterTaskPriority = 0u;
 // This allows a micro benchmark system to run tasks with highest priority,
 // since it should finish as quickly as possible.
 unsigned RasterWorkerPool::kBenchmarkRasterTaskPriority = 0u;

cc/resources/raster_worker_pool.h

@@ -16,7 +16,6 @@ namespace cc {
 
 class CC_EXPORT RasterWorkerPool {
  public:
-  static unsigned kOnDemandRasterTaskPriority;
   static unsigned kBenchmarkRasterTaskPriority;
   static unsigned kRasterFinishedTaskPriority;
   static unsigned kRasterTaskPriorityBase;