Clip PaintLayerScrollableArea::scrollIntoView return to layer bounds

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 1c356515a000fbe6f1ef14f2e71e5212e912f078..005e7121f129c27e30771e78c474ee5ae79bdaf7 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -1416,13 +1416,13 @@ LayoutRect PaintLayerScrollableArea::scrollIntoView(const LayoutRect& rect, cons
 
     DoublePoint clampedScrollPosition = clampScrollPosition(scrollPositionDouble() + roundedIntSize(r.location()));
     if (clampedScrollPosition == scrollPositionDouble())
-        return rect;
+        return LayoutRect(box().localToAbsoluteQuad(FloatQuad(FloatRect(intersection(layerBounds, localExposeRect))), UseTransforms).boundingBox());

[bokan, 2016/08/24 18:02:18]

Taking the intersection now means we might end up with an empty rect (this can
happen if the layer isn't being drawn or other edge cases). You should probably
handle that in LayoutBox::scrollRectToVisible by returning if the returned
|newRect| is empty.

 
     DoubleSize oldScrollOffset = adjustedScrollOffset();
     scrollToPosition(clampedScrollPosition, ScrollOffsetUnclamped, ScrollBehaviorInstant, scrollType);
     DoubleSize scrollOffsetDifference = adjustedScrollOffset() - oldScrollOffset;
     localExposeRect.move(-LayoutSize(scrollOffsetDifference));
-    return LayoutRect(box().localToAbsoluteQuad(FloatQuad(FloatRect(localExposeRect)), UseTransforms).boundingBox());
+    return LayoutRect(box().localToAbsoluteQuad(FloatQuad(FloatRect(intersection(layerBounds, localExposeRect))), UseTransforms).boundingBox());
 }
 
 void PaintLayerScrollableArea::updateScrollableAreaSet(bool hasOverflow)