Added support for the GL_TEXTURE_EXTERNAL target

This will allow us to support YUV surfaces.

Change-Id: I2d4da75f1006a5285bdc552695d4caeecccf2183
diff --git a/libs/surfaceflinger/LayerBlur.cpp b/libs/surfaceflinger/LayerBlur.cpp
index 4c8bae8..c1c440b 100644
--- a/libs/surfaceflinger/LayerBlur.cpp
+++ b/libs/surfaceflinger/LayerBlur.cpp
@@ -146,6 +146,9 @@
     Region::const_iterator it = clip.begin();
     Region::const_iterator const end = clip.end();
     if (it != end) {
+#if defined(GL_OES_texture_external)
+        glDisable(GL_TEXTURE_EXTERNAL_OES);
+#endif
         glEnable(GL_TEXTURE_2D);
         glBindTexture(GL_TEXTURE_2D, mTextureName);