Add support for direct EGLImageKHR use with pushbuffer API

We now always first try to use the EGLImageKHR directly before
making a copy with copybit. The copy may be needed when
EGLImage doesn't support the requested format, which is
currently the case with YUV.
diff --git a/libs/surfaceflinger/LayerBuffer.h b/libs/surfaceflinger/LayerBuffer.h
index e03f92c..3257b76 100644
--- a/libs/surfaceflinger/LayerBuffer.h
+++ b/libs/surfaceflinger/LayerBuffer.h
@@ -145,6 +145,7 @@
         mutable LayerBase::Texture      mTexture;
         mutable NativeBuffer            mTempBuffer;
         mutable sp<GraphicBuffer>       mTempGraphicBuffer;
+        mutable bool                    mUseEGLImageDirectly;
     };
     
     class OverlaySource : public Source {