Removed main-thread one dimensional scrolling paths.

third_party/WebKit/Source/core/frame/LocalFrame.cpp

Index: third_party/WebKit/Source/core/frame/LocalFrame.cpp
diff --git a/third_party/WebKit/Source/core/frame/LocalFrame.cpp b/third_party/WebKit/Source/core/frame/LocalFrame.cpp
index c66840f752db748376870248f9b453e0c43522d0..132bbf0c0acb488eb6c548fbc75d610801d2205a 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrame.cpp
+++ b/third_party/WebKit/Source/core/frame/LocalFrame.cpp
@@ -775,13 +775,6 @@ void LocalFrame::removeSpellingMarkersUnderWords(const Vector<String>& words)
     spellChecker().removeSpellingMarkersUnderWords(words);
 }
 
-static ScrollResult scrollAreaOnBothAxes(ScrollGranularity granularity, const FloatSize& delta, ScrollableArea& view)
-{
-    ScrollResultOneDimensional scrolledHorizontal = view.userScroll(ScrollLeft, granularity, delta.width());
-    ScrollResultOneDimensional scrolledVertical = view.userScroll(ScrollUp, granularity, delta.height());
-    return ScrollResult(scrolledHorizontal.didScroll, scrolledVertical.didScroll, scrolledHorizontal.unusedScrollDelta, scrolledVertical.unusedScrollDelta);
-}
-
 // Returns true if a scroll occurred.
 ScrollResult LocalFrame::applyScrollDelta(ScrollGranularity granularity, const FloatSize& delta, bool isScrollBegin)
 {
@@ -800,7 +793,13 @@ ScrollResult LocalFrame::applyScrollDelta(ScrollGranularity granularity, const F
     if (remainingDelta.isZero())
         return ScrollResult(delta.width(), delta.height(), 0.0f, 0.0f);
 
-    ScrollResult result = scrollAreaOnBothAxes(granularity, remainingDelta, *view()->scrollableArea());
+    // TODO(bokan): The delta coming in here is the GSU event delta, which is

[skobes, 2016/02/29 18:52:47]

what is GSU?

[bokan, 2016/03/01 05:56:24]

Sorry, forgot not everyone works on input :) (Gesture Scroll Update).

I've updated the wording.

+    // positive if the user scrolls up. For scrolling, a positive delta implies

[tdresser, 2016/02/29 14:53:43]

positive if the user scrolls up or left

[bokan, 2016/03/01 05:56:24]

Done.

+    // downward scrolling. This negation should happen up in the call chain.
+    FloatSize normalizedDelta = remainingDelta.scaledBy(-1);
+
+    ScrollResult result = view()->scrollableArea()->userScroll(granularity, normalizedDelta);
+
     result.didScrollX = result.didScrollX || (remainingDelta.width() != delta.width());
     result.didScrollY = result.didScrollY || (remainingDelta.height() != delta.height());