Don't call LayoutPart::widgetPositionsUpdated unnecessarily.

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@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 336 matching lines @@
     // compositing state, and remove this disabler.
     DisableCompositingQueryAsserts disabler;
 
     // Update the positions of our child layers (if needed as only fixed layers should be impacted by a scroll).
     // We don't update compositing layers, because we need to do a deep update from the compositing ancestor.
     if (!frameView->isInPerformLayout()) {
         // If we're in the middle of layout, we'll just update layers once layout has finished.
         layer()->updateLayerPositionsAfterOverflowScroll(scrollDelta);
         // Update regions, scrolling may change the clip of a particular region.
         frameView->updateDocumentAnnotatedRegions();
-        frameView->setNeedsUpdateWidgetPositions();
+        frameView->setNeedsUpdateWidgetGeometries();
         updateCompositingLayersAfterScroll();
     }
 
     const LayoutBoxModelObject& paintInvalidationContainer = box().containerForPaintInvalidation();
     // The caret rect needs to be invalidated after scrolling
     frame->selection().setCaretRectNeedsUpdate();
 
     FloatQuad quadForFakeMouseMoveEvent = FloatQuad(FloatRect(layer()->layoutObject()->previousPaintInvalidationRectIncludingCompositedScrolling(paintInvalidationContainer)));
 
     quadForFakeMouseMoveEvent = paintInvalidationContainer.localToAbsoluteQuad(quadForFakeMouseMoveEvent);
@@ skipping 1158 matching lines @@
 }
 
 DEFINE_TRACE(PaintLayerScrollableArea::ScrollbarManager)
 {
     visitor->trace(m_scrollableArea);
     visitor->trace(m_hBar);
     visitor->trace(m_vBar);
 }
 
 } // namespace blink