Revert of Initial version of external_oes texture support and unit test

src/gpu/gl/GrGLCaps.h

Index: src/gpu/gl/GrGLCaps.h
diff --git a/src/gpu/gl/GrGLCaps.h b/src/gpu/gl/GrGLCaps.h
index 0ec6c85b47ee8b846d5c6b9c85cf0c99965f7d9f..5f1ca3e340cad5bbf90bdc3e24995c8084fe4574 100644
--- a/src/gpu/gl/GrGLCaps.h
+++ b/src/gpu/gl/GrGLCaps.h
@@ -231,9 +231,6 @@
     bool bindFragDataLocationSupport() const { return fBindFragDataLocationSupport; }
 
     bool bindUniformLocationSupport() const { return fBindUniformLocationSupport; }
-
-    /// Are textures with GL_TEXTURE_EXTERNAL_OES type supported.
-    bool externalTextureSupport() const { return fExternalTextureSupport; }
 
     /**
      * Is there support for enabling/disabling sRGB writes for sRGB-capable color attachments?
@@ -363,7 +360,6 @@
     bool fRGBA8888PixelsOpsAreSlow : 1;
     bool fPartialFBOReadIsSlow : 1;
     bool fBindUniformLocationSupport : 1;
-    bool fExternalTextureSupport : 1;
 
     struct ReadPixelsSupportedFormat {
         GrGLenum fFormat;