Redelivering r3555 to re-add run-time switching between ANGLE and native opengl 

http://codereview.appspot.com/5969044/



git-svn-id: http://skia.googlecode.com/svn/trunk@3578 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/views/SkOSWindow_Unix.h b/include/views/SkOSWindow_Unix.h
index 3b71af8..40059bf 100644
--- a/include/views/SkOSWindow_Unix.h
+++ b/include/views/SkOSWindow_Unix.h
@@ -34,9 +34,15 @@
     void* getUnixWindow() const { return (void*)&fUnixWindow; }
     void loop();
     void post_linuxevent();
-    bool attachGL();
-    void detachGL();
-    void presentGL();
+
+    enum SkBackEndTypes {
+        kNone_BackEndType,
+        kNativeGL_BackEndType,
+    };
+
+    bool attach(SkBackEndTypes attachType);
+    void detach();
+    void present();
 
     //static bool PostEvent(SkEvent* evt, SkEventSinkID, SkMSec delay);