Force software rasterization on ThreadTimesCompositorCases benchmark.

tools/perf/benchmarks/silk_flags.py

Index: tools/perf/benchmarks/silk_flags.py
diff --git a/tools/perf/benchmarks/silk_flags.py b/tools/perf/benchmarks/silk_flags.py
index 5a4080e1a0869912ec1639baa0b518248c7e9173..b9338b9a4ab3d260b27dd1d7f22fa9454c32d363 100644
--- a/tools/perf/benchmarks/silk_flags.py
+++ b/tools/perf/benchmarks/silk_flags.py
@@ -6,6 +6,9 @@ def CustomizeBrowserOptionsForFastPath(options):
   """Enables flags needed for bleeding edge rendering fast paths."""
   options.AppendExtraBrowserArgs('--enable-bleeding-edge-rendering-fast-paths')
 
+def CustomizeBrowserOptionsForSoftwareRasterization(options):
+  """Enables flags needed for forced software rasterization."""
+  options.AppendExtraBrowserArgs('--disable-gpu-rasterization')
 
 def CustomizeBrowserOptionsForGpuRasterization(options):
   """Enables flags needed for forced GPU rasterization using Ganesh."""