Add hooks for hardware accelerated WebView.

Change-Id: I907cdec8a67594f87749ac46bda85f04af5a2003
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index 5748d57..d0e04b2 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -58,6 +58,8 @@
 
     void setViewport(int width, int height);
     void prepare();
+    void acquireContext();
+    void releaseContext();
 
     int getSaveCount() const;
     int save(int flags);