Move SkGLContext and some GrGLInterface implementations to skgputest module

src/gpu/gl/mesa/SkMesaGLContext.h

-/*
- * Copyright 2011 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-#ifndef SkMesaGLContext_DEFINED
-#define SkMesaGLContext_DEFINED
-
-#include "gl/SkGLContext.h"
-
-#if SK_MESA
-
-class SkMesaGLContext : public SkGLContext {
-private:
-    typedef intptr_t Context;
-
-public:
-    ~SkMesaGLContext() override;
-
-    static SkMesaGLContext* Create() {
-        SkMesaGLContext* ctx = new SkMesaGLContext;
-        if (!ctx->isValid()) {
-            delete ctx;
-            return nullptr;
-        }
-        return ctx;
-    }
-
-private:
-    SkMesaGLContext();
-    void destroyGLContext();
-
-    void onPlatformMakeCurrent() const override;
-    void onPlatformSwapBuffers() const override;
-    GrGLFuncPtr onPlatformGetProcAddress(const char*) const override;
-
-    Context fContext;
-    GrGLubyte *fImage;
-};
-
-#endif
-
-#endif