Revert of Initial version of external_oes texture support and unit test

src/gpu/glsl/GrGLSLCaps.h

Index: src/gpu/glsl/GrGLSLCaps.h
diff --git a/src/gpu/glsl/GrGLSLCaps.h b/src/gpu/glsl/GrGLSLCaps.h
index 9924773139c0610beae8caa3b5f725453f6c9bf7..68e91b6666599f543eedbc461649e98a4ecb02a5 100755
--- a/src/gpu/glsl/GrGLSLCaps.h
+++ b/src/gpu/glsl/GrGLSLCaps.h
@@ -102,10 +102,6 @@
         return fSecondaryOutputExtensionString;
     }
 
-    const char* externalTextureExtensionString() const {
-        return fExternalTextureExtensionString;
-    }
-
     bool mustSwizzleInShader() const { return fMustSwizzleInShader; }
 
     /**
@@ -144,7 +140,6 @@
     const char* fShaderDerivativeExtensionString;
     const char* fFragCoordConventionsExtensionString;
     const char* fSecondaryOutputExtensionString;
-    const char* fExternalTextureExtensionString;
 
     const char* fFBFetchColorName;
     const char* fFBFetchExtensionString;