Revert of Calculate paint invalidation rect for scrollbars

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

Index: third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h b/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
index f078c02a657b570e851d0aad5a1982ea0f4d0a91..35a072d2930b6de50133855c2797ad6ae4c599a5 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
@@ -62,6 +62,26 @@
 
     virtual bool invalidateOnMouseEnterExit() { return false; }
 
+    void invalidateParts(ScrollbarThemeClient* scrollbar, ScrollbarControlPartMask mask)
+    {
+        if (mask & BackButtonStartPart)
+            invalidatePart(scrollbar, BackButtonStartPart);
+        if (mask & ForwardButtonStartPart)
+            invalidatePart(scrollbar, ForwardButtonStartPart);
+        if (mask & BackTrackPart)
+            invalidatePart(scrollbar, BackTrackPart);
+        if (mask & ThumbPart)
+            invalidatePart(scrollbar, ThumbPart);
+        if (mask & ForwardTrackPart)
+            invalidatePart(scrollbar, ForwardTrackPart);
+        if (mask & BackButtonEndPart)
+            invalidatePart(scrollbar, BackButtonEndPart);
+        if (mask & ForwardButtonEndPart)
+            invalidatePart(scrollbar, ForwardButtonEndPart);
+    }
+
+    virtual void invalidatePart(ScrollbarThemeClient*, ScrollbarPart);
+
     virtual void paintScrollCorner(GraphicsContext*, const DisplayItemClientWrapper&, const IntRect& cornerRect);
     virtual void paintTickmarks(GraphicsContext*, const ScrollbarThemeClient*, const IntRect&) { }