Add flag to force touch events to be passive during fling as a runtime feature

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 272453f46e4b0af9ff441a5b64a8fae1438797c5..e0ba8f3828059173673e7f8af7f9ef5d073a7884 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -95,6 +95,11 @@ const base::Feature kParseHTMLOnMainThread{"ParseHTMLOnMainThread",
 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.
+const base::Feature kPassiveEventListenersDueToFling{
+    "PassiveEventListenersDueToFling", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Pointer events support.
 const base::Feature kPointerEvents{"PointerEvent",
                                    base::FEATURE_DISABLED_BY_DEFAULT};