Add a feature flag for enabling rendering pipeline throttling

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 f7e01a6be796c9719287a803bdceef5b0942bcc6..85d8abf2b042faac901742a2e38097758d6e19ef 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -208,6 +208,9 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
   if (!base::FeatureList::IsEnabled(features::kPaintOptimizations))
     WebRuntimeFeatures::enableFeatureFromString("PaintOptimizations", false);
 
+  WebRuntimeFeatures::enableRenderingPipelineThrottling(
+    base::FeatureList::IsEnabled(features::kRenderingPipelineThrottling));
+
   // Enable explicitly enabled features, and then disable explicitly disabled
   // ones.
   if (command_line.HasSwitch(switches::kEnableBlinkFeatures)) {