skia: Add support for ANGLE on linux

include/views/SkOSWindow_Unix.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkOSWindow_Unix_DEFINED
 #define SkOSWindow_Unix_DEFINED
 
@@ skipping 18 matching lines @@
     ~SkOSWindow();
 
     void* getHWND() const { return (void*)fUnixWindow.fWin; }
     void* getDisplay() const { return (void*)fUnixWindow.fDisplay; }
     void* getUnixWindow() const { return (void*)&fUnixWindow; }
     void loop();
 
     enum SkBackEndTypes {
         kNone_BackEndType,
         kNativeGL_BackEndType,
+#if SK_ANGLE
+        kANGLE_BackEndType,
+#endif // SK_ANGLE
     };
 
     bool attach(SkBackEndTypes attachType, int msaaSampleCount, AttachmentInfo*);
     void detach();
     void present();
 
     int getMSAASampleCount() const { return fMSAASampleCount; }
 
     //static bool PostEvent(SkEvent* evt, SkEventSinkID, SkMSec delay);
 
@@ skipping 25 matching lines @@
 
     // Needed for GL
     XVisualInfo* fVi;
     // we recreate the underlying xwindow if this changes
     int fMSAASampleCount;
 
     typedef SkWindow INHERITED;
 };
 
 #endif