Turn on the squashing runtime setting if specified on the commandline.

content/child/runtime_features.cc

Index: content/child/runtime_features.cc
diff --git a/content/child/runtime_features.cc b/content/child/runtime_features.cc
index e83576464c59f42d80b82b70bf9c417c83aa2f53..e39345c93bc7086aee86cf77370d340dda16d1b8 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -155,6 +155,9 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
 
   if (command_line.HasSwitch(switches::kEnablePreciseMemoryInfo))
     WebRuntimeFeatures::enablePreciseMemoryInfo(true);
+
+  if (command_line.HasSwitch(switches::kEnableLayerSquashing))
+    WebRuntimeFeatures::enableLayerSquashing(true);
 }
 
 }  // namespace content