Add runtime setting to force passive event listeners.

third_party/WebKit/public/web/WebSettings.h

Index: third_party/WebKit/public/web/WebSettings.h
diff --git a/third_party/WebKit/public/web/WebSettings.h b/third_party/WebKit/public/web/WebSettings.h
index f215571a484abbe5daa99c9b5486bbdbe07727c9..f905fd0f581852f03c133d4c8fa541360450621e 100644
--- a/third_party/WebKit/public/web/WebSettings.h
+++ b/third_party/WebKit/public/web/WebSettings.h
@@ -95,6 +95,15 @@ public:
         Subtitles
     };
 
+    // Defines the default for 'passive' field used in the AddEventListenerOptions interface
+    // when javascript calls addEventListener.
+    enum class PassiveEventListenerDefault {
+        False, // Default of false.
+        True, // Default of true.
+        DocumentTrue, // Default of true for document level elements, false otherwise.
+        ForceAllTrue // Force all values to be true even when specified.
+    };
+
     // Sets value of a setting by its string identifier from Settings.in and
     // string representation of value. An enum's string representation is the
     // string representation of the integer value of the enum.
@@ -184,6 +193,7 @@ public:
     virtual void setMinimumLogicalFontSize(int) = 0;
     virtual void setMockScrollbarsEnabled(bool) = 0;
     virtual void setOfflineWebApplicationCacheEnabled(bool) = 0;
+    virtual void setPassiveEventListenerDefault(PassiveEventListenerDefault) = 0;
     virtual void setPasswordEchoDurationInSeconds(double) = 0;
     virtual void setPasswordEchoEnabled(bool) = 0;
     virtual void setPerTilePaintingEnabled(bool) = 0;