Update RootFrameViewport::userScroll to distribute scrolls between viewports.

third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp

Index: third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
index 85016be74b5a15c2f326a65e4254a439ceac12f6..115084d24b88cc75ec3e03bf84f8def21bf542fb 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
@@ -131,19 +131,18 @@ GraphicsLayer* ScrollableArea::layerForContainer() const
     return layerForScrolling() ? layerForScrolling()->parent() : 0;
 }
 
-ScrollResultOneDimensional ScrollableArea::userScroll(ScrollDirectionPhysical direction, ScrollGranularity granularity, float delta)
+ScrollbarOrientation ScrollableArea::scrollbarOrientationFromDirection(ScrollDirectionPhysical direction)
 {
     ScrollbarOrientation orientation;
     if (direction == ScrollUp || direction == ScrollDown)
         orientation = VerticalScrollbar;

[bokan, 2015/12/04 20:42:52]

No need for the temp, just return VerticalScrollbar or HorizontalScrollbar

[ymalik, 2015/12/07 17:53:14]

Done.

     else
         orientation = HorizontalScrollbar;
+    return orientation;
+}
 
-    if (!userInputScrollable(orientation))
-        return ScrollResultOneDimensional(false, delta);
-
-    cancelProgrammaticScrollAnimation();
-
+float ScrollableArea::scrollStep(ScrollGranularity granularity, ScrollbarOrientation orientation) const
+{
     float step = 0;
     switch (granularity) {
     case ScrollByLine:
@@ -160,6 +159,18 @@ ScrollResultOneDimensional ScrollableArea::userScroll(ScrollDirectionPhysical di
         step = pixelStep(orientation);
         break;
     }
+    return step;
+}
+
+ScrollResultOneDimensional ScrollableArea::userScroll(ScrollDirectionPhysical direction, ScrollGranularity granularity, float delta)
+{
+    ScrollbarOrientation orientation = scrollbarOrientationFromDirection(direction);
+    if (!userInputScrollable(orientation))
+        return ScrollResultOneDimensional(false, delta);
+
+    cancelProgrammaticScrollAnimation();
+
+    float step = scrollStep(granularity, orientation);
 
     if (direction == ScrollUp || direction == ScrollLeft)
         delta = -delta;