Add a runtime flag in WebRuntimeFeatures to enable 'image/webp' accept header

Source/bindings/v8/RuntimeEnabledFeatures.h

Index: Source/bindings/v8/RuntimeEnabledFeatures.h
diff --git a/Source/bindings/v8/RuntimeEnabledFeatures.h b/Source/bindings/v8/RuntimeEnabledFeatures.h
index a17ae2346fe3976561fd845dadb9bb29f09e9711..dd6d95b5728ea8ba06867a17173edf2aba67c8b3 100644
--- a/Source/bindings/v8/RuntimeEnabledFeatures.h
+++ b/Source/bindings/v8/RuntimeEnabledFeatures.h
@@ -248,6 +248,11 @@ public:
     static bool requestAutocompleteEnabled() { return isRequestAutocompleteEnabled; }
     static void setRequestAutocompleteEnabled(bool isEnabled) { isRequestAutocompleteEnabled = isEnabled; }
 
+#if USE(WEBP)
+    static void setWebPInAcceptHeaderEnabled(bool isEnabled) { isWebPInAcceptHeaderEnabled = isEnabled; }
+    static bool webPInAcceptHeaderEnabled() { return isWebPInAcceptHeaderEnabled; }
+#endif
+
 private:
     // Never instantiate.
     RuntimeEnabledFeatures() { }
@@ -333,6 +338,10 @@ private:
 
     static bool isDoNotTrackEnabled;
 
+#if USE(WEBP)
+    static bool isWebPInAcceptHeaderEnabled;
+#endif
+
 };
 
 } // namespace WebCore