Move SkGLContext and some GrGLInterface implementations to skgputest module

src/gpu/gl/GrGLTestInterface.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLTestInterface_DEFINED
 #define GrGLTestInterface_DEFINED
 
 #include "gl/GrGLInterface.h"
 #include "GrGLDefines.h"
 
+/**
+ * Base class for interfaces used for Skia testing. We would like to move this to tools/gpu/gl
+ * when Chromium is no longer using GrGLCreateNullInterface in its unit testing.
+ */
 class GrGLTestInterface : public GrGLInterface {
 public:
     virtual GrGLvoid activeTexture(GrGLenum texture) {}
     virtual GrGLvoid attachShader(GrGLuint program, GrGLuint shader) {}
     virtual GrGLvoid beginQuery(GrGLenum target, GrGLuint id) {}
     virtual GrGLvoid bindAttribLocation(GrGLuint program, GrGLuint index, const char* name) {}
     virtual GrGLvoid bindBuffer(GrGLenum target, GrGLuint buffer) {}
     virtual GrGLvoid bindFramebuffer(GrGLenum target, GrGLuint framebuffer) {}
     virtual GrGLvoid bindRenderbuffer(GrGLenum target, GrGLuint renderbuffer) {}
     virtual GrGLvoid bindTexture(GrGLenum target, GrGLuint texture) {}
@@ skipping 300 matching lines @@
     // This must be called by leaf class
     void init(GrGLStandard standard) {
         fStandard = standard;
         fExtensions.init(standard, fFunctions.fGetString, fFunctions.fGetStringi,
                          fFunctions.fGetIntegerv, nullptr, GR_EGL_NO_DISPLAY);
     }
     GrGLTestInterface();
 };
 
 #endif