Delete a bunch of noop paint invalidation code.

sky/engine/platform/HostWindow.h

Index: sky/engine/platform/HostWindow.h
diff --git a/sky/engine/platform/HostWindow.h b/sky/engine/platform/HostWindow.h
index 266bef5401d4ff1b3091a39fdd4bbc503fc6245c..d8b46edd6b00f8104ebcd131dfe96e34be50c9f9 100644
--- a/sky/engine/platform/HostWindow.h
+++ b/sky/engine/platform/HostWindow.h
@@ -40,12 +40,6 @@ public:
     HostWindow() { }
     virtual ~HostWindow() { }
 
-    // Requests the host invalidate the contents and the root view.
-    virtual void invalidateContentsAndRootView(const IntRect& updateRect) = 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;
-
     // Methods for doing coordinate conversions to screen coordinates.
     virtual IntRect rootViewToScreen(const IntRect&) const = 0;