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

third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h

Index: third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
index c9087c69739672216ed86c823269d9af8009aebc..0af2c0444fc2d0c34e8b2978d7d5b034e8dd9665 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
@@ -45,21 +45,22 @@ public:
     int scrollbarMargin() const override;
     bool usesOverlayScrollbars() const override;
 
-    int thumbPosition(const ScrollbarThemeClient*) override;
-    int thumbLength(const ScrollbarThemeClient*) override;
+    int thumbPosition(const ScrollbarThemeClient&) override;
+    int thumbLength(const ScrollbarThemeClient&) override;
 
-    bool hasButtons(const ScrollbarThemeClient*) override { return false; }
-    bool hasThumb(const ScrollbarThemeClient*) override;
+    bool hasButtons(const ScrollbarThemeClient&) override { return false; }
+    bool hasThumb(const ScrollbarThemeClient&) override;
 
-    IntRect backButtonRect(const ScrollbarThemeClient*, ScrollbarPart, bool painting = false) override;
-    IntRect forwardButtonRect(const ScrollbarThemeClient*, ScrollbarPart, bool painting = false) override;
-    IntRect trackRect(const ScrollbarThemeClient*, bool painting = false) override;
-    int thumbThickness(const ScrollbarThemeClient*) override;
+    IntRect backButtonRect(const ScrollbarThemeClient&, ScrollbarPart, bool painting = false) override;
+    IntRect forwardButtonRect(const ScrollbarThemeClient&, ScrollbarPart, bool painting = false) override;
+    IntRect trackRect(const ScrollbarThemeClient&, bool painting = false) override;
+    int thumbThickness(const ScrollbarThemeClient&) override;
+    int thumbThickness() { return m_thumbThickness; }

[Xianzhu, 2015/12/09 17:26:49]

The caller (VisualViewport::setupScrollbar()) need to get thumb thickness
setting before creating the actual scrollbar, but
ScrollbarTheme::thumbThickness() requires a scrollbar to calculate the
thickness. Add this method to allow callers to access the setting without a
scrollbar.

 
-    void paintThumb(GraphicsContext*, const ScrollbarThemeClient*, const IntRect&) override;
-    ScrollbarPart hitTest(const ScrollbarThemeClient*, const IntPoint&) override;
+    void paintThumb(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&) override;
+    ScrollbarPart hitTest(const ScrollbarThemeClient&, const IntPoint&) override;
 
-    static ScrollbarTheme* mobileTheme();
+    static ScrollbarThemeOverlay& mobileTheme();

[Xianzhu, 2015/12/09 17:26:49]

This allows callers to access thumbThickness().

 
 private:
     int m_thumbThickness;