Remove devtools_instrumentation::kRasterTask in favor of frame viewer's one

cc/debug/devtools_instrumentation.h

 // 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.
 
 #ifndef CC_DEBUG_DEVTOOLS_INSTRUMENTATION_H_
 #define CC_DEBUG_DEVTOOLS_INSTRUMENTATION_H_
 
 #include "base/debug/trace_event.h"
 
 namespace cc {
 namespace devtools_instrumentation {
 
 namespace internal {
 const char kCategory[] = TRACE_DISABLED_BY_DEFAULT("devtools.timeline");
 const char kCategoryFrame[] =
     TRACE_DISABLED_BY_DEFAULT("devtools.timeline.frame");
 const char kFrameId[] = "frameId";
 const char kLayerId[] = "layerId";
 const char kLayerTreeId[] = "layerTreeId";
 const char kPixelRefId[] = "pixelRefId";
 
 const char kImageDecodeTask[] = "ImageDecodeTask";
 const char kBeginFrame[] = "BeginFrame";
 const char kActivateLayerTree[] = "ActivateLayerTree";
 const char kRequestMainThreadFrame[] = "RequestMainThreadFrame";
 const char kDrawFrame[] = "DrawFrame";
 }  // namespace internal
 
-const char kRasterTask[] = "RasterTask";
 const char kPaintSetup[] = "PaintSetup";
 const char kUpdateLayer[] = "UpdateLayer";
 
 class ScopedLayerTask {
  public:
   ScopedLayerTask(const char* event_name, int layer_id)
     : event_name_(event_name) {
     TRACE_EVENT_BEGIN1(internal::kCategory, event_name_,
         internal::kLayerId, layer_id);
   }
@@ skipping 82 matching lines @@
                        internal::kRequestMainThreadFrame,
                        TRACE_EVENT_SCOPE_THREAD,
                        internal::kLayerTreeId,
                        layer_tree_host_id);
 }
 
 }  // namespace devtools_instrumentation
 }  // namespace cc
 
 #endif  // CC_DEBUG_DEVTOOLS_INSTRUMENTATION_H_