Add rasterize_and_record_micro.fast_path_gpu_rasterization.key_silk_cases benchmark

tools/perf/benchmarks/repaint.py

 # Copyright 2014 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.
 
+from benchmarks import silk_flags
 from measurements import repaint
 from telemetry import test
 
 
 class RepaintKeyMobileSites(test.Test):
   """Measures repaint performance on the key mobile sites.
 
   http://www.chromium.org/developers/design-documents/rendering-benchmarks"""
   test = repaint.Repaint
   page_set = 'page_sets/key_mobile_sites.py'
 
 
 class RepaintGpuRasterizationKeyMobileSites(test.Test):
   """Measures repaint performance on the key mobile sites with forced GPU
   rasterization.
 
   http://www.chromium.org/developers/design-documents/rendering-benchmarks"""
   tag = 'gpu_rasterization'
   test = repaint.Repaint
   page_set = 'page_sets/key_mobile_sites.py'
   def CustomizeBrowserOptions(self, options):
-    options.AppendExtraBrowserArgs('--enable-threaded-compositing')
-    options.AppendExtraBrowserArgs('--force-compositing-mode')
-    options.AppendExtraBrowserArgs('--enable-impl-side-painting')
-    options.AppendExtraBrowserArgs('--force-gpu-rasterization')
+    silk_flags.CustomizeBrowserOptionsForGpuRasterization(options)