Implement top controls show/hide functionality for main thread scrolling

Source/web/WebInputEventConversion.cpp

Index: Source/web/WebInputEventConversion.cpp
diff --git a/Source/web/WebInputEventConversion.cpp b/Source/web/WebInputEventConversion.cpp
index a4a3afa831a8f3cc69bf6cb805cc64fcfe59a630..3a6735fd33409cc00045087b612ec763736f110b 100644
--- a/Source/web/WebInputEventConversion.cpp
+++ b/Source/web/WebInputEventConversion.cpp
@@ -289,6 +289,17 @@ PlatformGestureEventBuilder::PlatformGestureEventBuilder(Widget* widget, const W
     m_modifiers = toPlatformEventModifiers(e.modifiers);
 }
 
+
+PlatformGestureEventBuilder::PlatformGestureEventBuilder(Widget* widget, const WebGestureEvent& e, float deltaX, float deltaY)
+    : PlatformGestureEventBuilder(widget, e)
+{
+    if (m_type == PlatformEvent::GestureScrollUpdate) {
+        m_data.m_scrollUpdate.m_deltaX = deltaX;
+        m_data.m_scrollUpdate.m_deltaY = deltaY;
+    }
+}
+
+
 // MakePlatformKeyboardEvent --------------------------------------------------
 
 inline PlatformEvent::Type toPlatformKeyboardEventType(WebInputEvent::Type type)