Put WebViews with on a HW layer if stencil/shader clipping is needed

bug:17322378
Change-Id: I0de574bf116b30e2ad4194366e19d47d49708902
diff --git a/libs/hwui/CanvasState.h b/libs/hwui/CanvasState.h
index 9354e94..b35db28 100644
--- a/libs/hwui/CanvasState.h
+++ b/libs/hwui/CanvasState.h
@@ -155,8 +155,9 @@
     inline bool currentlyIgnored() const { return currentSnapshot()->isIgnored(); }
     int getViewportWidth() const { return currentSnapshot()->getViewportWidth(); }
     int getViewportHeight() const { return currentSnapshot()->getViewportHeight(); }
-    int getWidth() { return mWidth; }
-    int getHeight() { return mHeight; }
+    int getWidth() const { return mWidth; }
+    int getHeight() const { return mHeight; }
+    bool clipIsSimple() const { return currentSnapshot()->clipIsSimple(); }
 
     inline const Snapshot* currentSnapshot() const {
         return mSnapshot != nullptr ? mSnapshot.get() : mFirstSnapshot.get();