Revert of Make the Sk GL context class an abstract base class

include/gpu/gl/SkGLContextHelper.h

Index: include/gpu/gl/SkGLContextHelper.h
diff --git a/include/gpu/gl/SkGLContextHelper.h b/include/gpu/gl/SkGLContextHelper.h
new file mode 100644
index 0000000000000000000000000000000000000000..c4d9bdf9979c4165cd67f404d708711b0f716291
--- /dev/null
+++ b/include/gpu/gl/SkGLContextHelper.h
@@ -0,0 +1,95 @@
+
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef SkGLContextHelper_DEFINED
+#define SkGLContextHelper_DEFINED
+
+#include "GrGLInterface.h"
+
+/**
+ * Create an offscreen opengl context with an RGBA8 / 8bit stencil FBO.
+ * Provides a GrGLInterface struct of function pointers for the context.
+ */
+
+class SK_API SkGLContextHelper : public SkRefCnt {
+public:
+    SK_DECLARE_INST_COUNT(SkGLContextHelper)
+
+    SkGLContextHelper();
+    virtual ~SkGLContextHelper();
+
+    /**
+     * Initializes the context and makes it current.
+     */
+    bool init(GrGLStandard forcedGpuAPI, const int width, const int height);
+
+    int getFBOID() const { return fFBO; }
+
+    const GrGLInterface* gl() const { return fGL; }
+
+    virtual void makeCurrent() const = 0;
+
+    /**
+     * The primary purpose of this function it to provide a means of scheduling
+     * work on the GPU (since all of the subclasses create primary buffers for
+     * testing that are small and not meant to be rendered to the screen).
+     *
+     * If the drawing surface provided by the platform is double buffered this
+     * call will cause the platform to swap which buffer is currently being
+     * targeted.  If the current surface does not include a back buffer, this
+     * call has no effect.
+     */
+    virtual void swapBuffers() const = 0;
+
+    bool hasExtension(const char* extensionName) const {
+        SkASSERT(fGL);
+        return fGL->hasExtension(extensionName);
+    }
+
+    /**
+     * This notifies the context that we are deliberately testing abandoning
+     * the context. It is useful for debugging contexts that would otherwise
+     * test that GPU resources are properly deleted. It also allows a debugging
+     * context to test that further GL calls are not made by Skia GPU code.
+     */
+    void testAbandon();
+
+protected:
+    /**
+     * Subclass implements this to make a GL context. The returned GrGLInterface
+     * should be populated with functions compatible with the context. The
+     * format and size of backbuffers does not matter since an FBO will be
+     * created.
+     */
+    virtual const GrGLInterface* createGLContext(GrGLStandard forcedGpuAPI) = 0;
+
+    /**
+     * Subclass should destroy the underlying GL context.
+     */
+    virtual void destroyGLContext() = 0;
+
+private:
+    GrGLuint fFBO;
+    GrGLuint fColorBufferID;
+    GrGLuint fDepthStencilBufferID;
+    const GrGLInterface* fGL;
+
+    typedef SkRefCnt INHERITED;
+};
+
+/**
+ * Helper macros for using the GL context through the GrGLInterface. Example:
+ * SK_GL(glCtx, GenTextures(1, &texID));
+ */
+#define SK_GL(ctx, X) (ctx).gl()->fFunctions.f ## X;    \
+                      SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
+#define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X;    \
+                  SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
+#define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->fFunctions.f ## X
+#define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X
+
+#endif