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

third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.mm

Index: third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.mm
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.mm b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.mm
index 4ab88e4c5d03555885ac312f9d8ea33346cab3e8..1d39d75311c7075e0928096eb4e022ef01747df9 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.mm
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.mm
@@ -56,7 +56,7 @@ using namespace blink;
 
 namespace blink {
 
-typedef HashSet<ScrollbarThemeClient*> ScrollbarSet;
+typedef HashSet<ScrollbarThemeClient&> ScrollbarSet;
 
 static ScrollbarSet& scrollbarSet()
 {
@@ -71,32 +71,29 @@ static bool gScrollAnimationEnabledForSystem = false;
 
 ScrollbarTheme* ScrollbarTheme::nativeTheme()
 {
-    static ScrollbarThemeMacCommon* theme = NULL;
-    if (theme)
-        return theme;
     if (ScrollbarThemeMacCommon::isOverlayAPIAvailable()) {
         DEFINE_STATIC_LOCAL(ScrollbarThemeMacOverlayAPI, overlayTheme, ());
-        theme = &overlayTheme;
-    } else {
+        return overlayTheme;
+    }
+    {
         DEFINE_STATIC_LOCAL(ScrollbarThemeMacNonOverlayAPI, nonOverlayTheme, ());
-        theme = &nonOverlayTheme;
+        return nonOverlayTheme;
     }
-    return theme;
 }
 
-void ScrollbarThemeMacCommon::registerScrollbar(ScrollbarThemeClient* scrollbar)
+void ScrollbarThemeMacCommon::registerScrollbar(ScrollbarThemeClient& scrollbar)
 {
     scrollbarSet().add(scrollbar);
 }
 
-void ScrollbarThemeMacCommon::unregisterScrollbar(ScrollbarThemeClient* scrollbar)
+void ScrollbarThemeMacCommon::unregisterScrollbar(ScrollbarThemeClient& scrollbar)
 {
     scrollbarSet().remove(scrollbar);
 }
 
-void ScrollbarThemeMacCommon::paintGivenTickmarks(SkCanvas* canvas, const ScrollbarThemeClient* scrollbar, const IntRect& rect, const Vector<IntRect>& tickmarks)
+void ScrollbarThemeMacCommon::paintGivenTickmarks(SkCanvas* canvas, const ScrollbarThemeClient& scrollbar, const IntRect& rect, const Vector<IntRect>& tickmarks)
 {
-    if (scrollbar->orientation() != VerticalScrollbar)
+    if (scrollbar.orientation() != VerticalScrollbar)
         return;
 
     if (rect.height() <= 0 || rect.width() <= 0)
@@ -119,7 +116,7 @@ void ScrollbarThemeMacCommon::paintGivenTickmarks(SkCanvas* canvas, const Scroll
 
     for (Vector<IntRect>::const_iterator i = tickmarks.begin(); i != tickmarks.end(); ++i) {
         // Calculate how far down (in %) the tick-mark should appear.
-        const float percent = static_cast<float>(i->y()) / scrollbar->totalSize();
+        const float percent = static_cast<float>(i->y()) / scrollbar.totalSize();
         if (percent < 0.0 || percent > 1.0)
             continue;
 
@@ -133,17 +130,17 @@ void ScrollbarThemeMacCommon::paintGivenTickmarks(SkCanvas* canvas, const Scroll
     }
 }
 
-void ScrollbarThemeMacCommon::paintTickmarks(GraphicsContext* context, const ScrollbarThemeClient* scrollbar, const IntRect& rect)
+void ScrollbarThemeMacCommon::paintTickmarks(GraphicsContext& context, const ScrollbarThemeClient& scrollbar, const IntRect& rect)
 {
     // Note: This is only used for css-styled scrollbars on mac.
-    if (scrollbar->orientation() != VerticalScrollbar)
+    if (scrollbar.orientation() != VerticalScrollbar)
         return;
 
     if (rect.height() <= 0 || rect.width() <= 0)
         return;
 
     Vector<IntRect> tickmarks;
-    scrollbar->getTickmarks(tickmarks);
+    scrollbar.getTickmarks(tickmarks);
     if (!tickmarks.size())
         return;
 
@@ -201,7 +198,7 @@ double ScrollbarThemeMacCommon::autoscrollTimerDelay()
     return gAutoscrollButtonDelay;
 }
 
-bool ScrollbarThemeMacCommon::shouldDragDocumentInsteadOfThumb(const ScrollbarThemeClient*, const PlatformMouseEvent& event)
+bool ScrollbarThemeMacCommon::shouldDragDocumentInsteadOfThumb(const ScrollbarThemeClient&, const PlatformMouseEvent& event)
 {
     return event.altKey();
 }