Only clear tooltip message on a user scroll or compositor scroll.

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 395 matching lines @@
 
   FloatQuad quadForFakeMouseMoveEvent = FloatQuad(FloatRect(
       layer()->layoutObject()->previousVisualRectIncludingCompositedScrolling(
           paintInvalidationContainer)));
 
   quadForFakeMouseMoveEvent =
       paintInvalidationContainer.localToAbsoluteQuad(quadForFakeMouseMoveEvent);
   frame->eventHandler().dispatchFakeMouseMoveEventSoonInQuad(
       quadForFakeMouseMoveEvent);
 
-  Page* page = frame->page();
-  if (page)
-    page->chromeClient().clearToolTip(*frame);
+  if (scrollType == UserScroll || scrollType == CompositorScroll) {
+    if (Page* page = frame->page())

[tdresser, 2017/01/03 13:56:32]

Why move this assignment into the conditional?

[szager1, 2017/01/03 20:24:22]

I have no opinion on this.  I restored the previous syntax.

[bokan, 2017/01/04 23:53:09]

No need to change anything again, just FYI, but I seem to recall Blink style at
one point encouraging this (though I can't find it now) and there's lots of
precedent in existing code. The advantage is that it limits the scope on a
variable to where its used.

+      page->chromeClient().clearToolTip(*frame);
+  }
 
   bool requiresPaintInvalidation = true;
 
   if (box().view()->compositor()->inCompositingMode()) {
     bool onlyScrolledCompositedLayers =
         scrollsOverflow() && layer()->isAllScrollingContentComposited() &&
         box().style()->backgroundLayers().attachment() !=
             LocalBackgroundAttachment;
 
     if (usesCompositedScrolling() || onlyScrolledCompositedLayers)
@@ skipping 1643 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetAfterOverflowChange();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink