Add partial damage support to new draw path

Change-Id: I612578fd181240de71297c9a28bc9a8f350764a7
diff --git a/libs/hwui/renderthread/CanvasContext.h b/libs/hwui/renderthread/CanvasContext.h
index e0cbabd..16956e6 100644
--- a/libs/hwui/renderthread/CanvasContext.h
+++ b/libs/hwui/renderthread/CanvasContext.h
@@ -141,6 +141,9 @@
 
     void freePrefetechedLayers();
 
+    int lastFrameWidth = 0;
+    int lastFrameHeight = 0;
+
     RenderThread& mRenderThread;
     EglManager& mEglManager;
     sp<ANativeWindow> mNativeWindow;