Use refs for non-null GraphicsContext, Scrollbar, etc. in scrollbar related code

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

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 192 matching lines @@
     if (scale != m_scale) {
         m_scale = scale;
         valuesChanged = true;
         frameHost().chromeClient().pageScaleFactorChanged();
     }
 
     FloatPoint clampedOffset(clampOffsetToBoundaries(location));
 
     if (clampedOffset != m_offset) {
         m_offset = clampedOffset;
-        scrollAnimator()->setCurrentPosition(m_offset);
+        scrollAnimator().setCurrentPosition(m_offset);
 
         // SVG runs with accelerated compositing disabled so no ScrollingCoordinator.
         if (ScrollingCoordinator* coordinator = frameHost().page().scrollingCoordinator())
             coordinator->scrollableAreaScrollLayerDidChange(this);
 
         if (!frameHost().settings().inertVisualViewport()) {
             if (Document* document = mainFrame()->document())
                 document->enqueueScrollEventForNode(document);
         }
 
@@ skipping 133 matching lines @@
 }
 
 void VisualViewport::setupScrollbar(WebScrollbar::Orientation orientation)
 {
     bool isHorizontal = orientation == WebScrollbar::Horizontal;
     GraphicsLayer* scrollbarGraphicsLayer = isHorizontal ?
         m_overlayScrollbarHorizontal.get() : m_overlayScrollbarVertical.get();
     OwnPtr<WebScrollbarLayer>& webScrollbarLayer = isHorizontal ?
         m_webOverlayScrollbarHorizontal : m_webOverlayScrollbarVertical;
 
-    ScrollbarTheme* theme = ScrollbarThemeOverlay::mobileTheme();
-    int thumbThickness = theme->thumbThickness(0);
-    int scrollbarThickness = theme->scrollbarThickness(RegularScrollbar);
-    int scrollbarMargin = theme->scrollbarMargin();
+    ScrollbarThemeOverlay& theme = ScrollbarThemeOverlay::mobileTheme();
+    int thumbThickness = theme.thumbThickness();
+    int scrollbarThickness = theme.scrollbarThickness(RegularScrollbar);
+    int scrollbarMargin = theme.scrollbarMargin();
 
     if (!webScrollbarLayer) {
         ScrollingCoordinator* coordinator = frameHost().page().scrollingCoordinator();
         ASSERT(coordinator);
         ScrollbarOrientation webcoreOrientation = isHorizontal ? HorizontalScrollbar : VerticalScrollbar;
         webScrollbarLayer = coordinator->createSolidColorScrollbarLayer(webcoreOrientation, thumbThickness, scrollbarMargin, false);
 
         // The compositor will control the scrollbar's visibility. Set to invisible by defualt
         // so scrollbars don't show up in layout tests.
         webScrollbarLayer->layer()->setOpacity(0);
@@ skipping 355 matching lines @@
     } else if (graphicsLayer == m_rootTransformLayer) {
         name =  "Root Transform Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink