Remove some dead scrolling paths and unused params

Source/platform/HostWindow.h

Index: Source/platform/HostWindow.h
diff --git a/Source/platform/HostWindow.h b/Source/platform/HostWindow.h
index fd7e098ff35d450a98b1117fed5226c2f1e2fc24..7744e3f1f5bc36b54b8dd2326c94fb24789c8884 100644
--- a/Source/platform/HostWindow.h
+++ b/Source/platform/HostWindow.h
@@ -49,8 +49,7 @@ public:
     // Requests the host invalidate the contents and the root view.
     virtual void invalidateContentsAndRootView(const IntRect& updateRect) = 0;
 
-    // Requests the host scroll backingstore by the specified delta, rect to scroll, and clip rect.
-    virtual void scroll(const IntSize& scrollDelta, const IntRect& rectToScroll, const IntRect& clipRect) = 0;
+    virtual void scroll(const IntRect& clipRect) = 0;
 
     // Requests the host invalidate the contents, not the root view. This is the slow path for scrolling.
     virtual void invalidateContentsForSlowScroll(const IntRect& updateRect) = 0;