Scroll the position into view when the content is not visible.

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 42bae0b72a85e2141f46a13709ba8223a6526927..78d933821253a531db8af12f76e71b5089ae3247 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -86,6 +86,12 @@
 
 namespace blink {
 
+static LayoutRect localToAbsolute(LayoutBox& offset, LayoutRect rect) {
+  return LayoutRect(
+      offset.localToAbsoluteQuad(FloatQuad(FloatRect(rect)), UseTransforms)
+          .boundingBox());
+}
+
 PaintLayerScrollableAreaRareData::PaintLayerScrollableAreaRareData() {}
 
 const int ResizerControlExpandRatioForTouch = 2;
@@ -1645,23 +1651,25 @@ LayoutRect PaintLayerScrollableArea::scrollIntoView(
       toScrollOffset(FloatPoint(r.location()) + oldScrollOffset))));
 
   if (newScrollOffset == oldScrollOffset) {
-    return LayoutRect(
-        box()
-            .localToAbsoluteQuad(FloatQuad(FloatRect(intersection(
-                                     layerBounds, localExposeRect))),
-                                 UseTransforms)
-            .boundingBox());
+    LayoutRect intersect =

[bokan, 2016/12/20 15:43:56]

This part is duplicated below. I think the three lines following this block are
no-op if newScrollOffset == oldScrollOffset so I don't think we need this block
at all? Otherwise just wrap them in `if (newScrollOffset != oldScrollOffset)`
instead and remove this block.

[sunyunjia, 2017/01/04 19:32:37]

Done.

+        localToAbsolute(box(), intersection(layerBounds, localExposeRect));
+    if (intersect.isEmpty() && !layerBounds.isEmpty() &&
+        !localExposeRect.isEmpty()) {
+      return localToAbsolute(box(), localExposeRect);
+    }
+    return intersect;
   }
 
   setScrollOffset(newScrollOffset, scrollType, ScrollBehaviorInstant);
   ScrollOffset scrollOffsetDifference = getScrollOffset() - oldScrollOffset;
   localExposeRect.move(-LayoutSize(scrollOffsetDifference));
-  return LayoutRect(
-      box()
-          .localToAbsoluteQuad(
-              FloatQuad(FloatRect(intersection(layerBounds, localExposeRect))),
-              UseTransforms)
-          .boundingBox());
+  LayoutRect intersect =
+      localToAbsolute(box(), intersection(layerBounds, localExposeRect));
+  if (intersect.isEmpty() && !layerBounds.isEmpty() &&
+      !localExposeRect.isEmpty()) {
+    return localToAbsolute(box(), localExposeRect);
+  }
+  return intersect;
 }
 
 void PaintLayerScrollableArea::updateScrollableAreaSet(bool hasOverflow) {