Add rasterize_and_record_micro.fast_path_gpu_rasterization.key_silk_cases benchmark

tools/perf/benchmarks/smoothness.py

Index: tools/perf/benchmarks/smoothness.py
diff --git a/tools/perf/benchmarks/smoothness.py b/tools/perf/benchmarks/smoothness.py
index f0e2ed760869fe6f5a0612f08dedfc23f2bb95ef..36c56fce27dc6c16c88b503fbbfd68ffb18ed0ee 100644
--- a/tools/perf/benchmarks/smoothness.py
+++ b/tools/perf/benchmarks/smoothness.py
@@ -71,10 +71,7 @@ class SmoothnessGpuRasterizationTop25(test.Test):
   test = smoothness.Smoothness
   page_set = 'page_sets/top_25.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)
 
 
 class SmoothnessGpuRasterizationKeyMobileSites(test.Test):
@@ -85,10 +82,7 @@ class SmoothnessGpuRasterizationKeyMobileSites(test.Test):
   test = smoothness.Smoothness
   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)
 
 
 class SmoothnessGpuRasterizationKeySilkCases(test.Test):
@@ -98,10 +92,7 @@ class SmoothnessGpuRasterizationKeySilkCases(test.Test):
   test = smoothness.Smoothness
   page_set = 'page_sets/key_silk_cases.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)
 
 
 class SmoothnessFastPathGpuRasterizationKeySilkCases(