Move SkGLContext and some GrGLInterface implementations to skgputest module

tools/gpu/gl/null/NullGLContext.cpp

+
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "NullGLContext.h"
+#include "gl/GrGLInterface.h"
+
+// TODO: Move the GrGLCreateNullInterface implementation here when Chromium is no longer using it
+// in its implementation.
+
+namespace {
+class NullGLContext : public sk_gpu_test::GLContext {
+public:
+    NullGLContext() { this->init(GrGLCreateNullInterface()); }
+   ~NullGLContext() override { this->teardown(); }
+
+private:    
+    void onPlatformMakeCurrent() const override {};
+    void onPlatformSwapBuffers() const override {}
+    GrGLFuncPtr onPlatformGetProcAddress(const char*) const override { return nullptr; }
+};
+}  // anonymous namespace
+
+namespace sk_gpu_test {
+GLContext* CreateNullGLContext() {
+    GLContext* ctx = new NullGLContext();
+    if (ctx->isValid()) {
+        return ctx;
+    }
+    delete ctx;
+    return nullptr;
+}
+}  // namespace sk_gpu_test
+