Enabled partial swap support for software compositing.

cc/software_renderer.h

Index: cc/software_renderer.h
diff --git a/cc/software_renderer.h b/cc/software_renderer.h
index 4bcfc3cb5726c830bd92b03a37704e16081e925d..5b9baa4ddd3141fa3907b08000bab5c070c5a58e 100644
--- a/cc/software_renderer.h
+++ b/cc/software_renderer.h
@@ -55,6 +55,8 @@ protected:
 private:
     SoftwareRenderer(RendererClient*, ResourceProvider*, SoftwareOutputDevice*);
 
+    void clearCanvas(SkColor color);
+    void setClipRect(const gfx::Rect& rect);
     bool isSoftwareResource(ResourceProvider::ResourceId) const;
 
     void drawDebugBorderQuad(const DrawingFrame&, const DebugBorderDrawQuad*);
@@ -66,6 +68,8 @@ private:
 
     RendererCapabilities m_capabilities;
     bool m_visible;
+    bool m_isScissorEnabled;
+    gfx::Rect m_scissorRect;
 
     SoftwareOutputDevice* m_outputDevice;
     scoped_ptr<SkCanvas> m_skRootCanvas;