Force events to be non blocking if main thread is unresponsive.

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 5e28c3f52aca23b5c2eaf86e58803b7302c1285f..54351d1222d1753290282600918f06c8ee1a4d44 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -67,6 +67,11 @@ const base::Feature kMediaDocumentDownloadButton{
 const base::Feature kNewMediaPlaybackUi{"NewMediaPlaybackUi",
                                         base::FEATURE_ENABLED_BY_DEFAULT};
 
+// An experiment forcing events to be non-blocking when the main thread is
+// deemed unresponsive.  See crbug.com/599609.
+const base::Feature kMainThreadBusyScrollIntervention{
+    "MainThreadBusyScrollIntervention", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Non-validating reload for desktop.
 // See https://crbug.com/591245
 const base::Feature kNonValidatingReloadOnNormalReload{
@@ -101,7 +106,7 @@ const base::Feature kPassiveDocumentEventListeners{
     "PassiveDocumentEventListeners", base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Whether we should force a touchstart and first touchmove per scroll event
-// listeners to be 'passive' during fling.
+// listeners to be non-blocking during fling.
 const base::Feature kPassiveEventListenersDueToFling{
     "PassiveEventListenersDueToFling", base::FEATURE_DISABLED_BY_DEFAULT};