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

include/gpu/gl/SkMesaGLContext.h

Index: include/gpu/gl/SkMesaGLContext.h
diff --git a/include/gpu/gl/SkMesaGLContext.h b/include/gpu/gl/SkMesaGLContext.h
index ef0017180c699d33dee464c62de35763f1a8433c..28349ddd8880600ab9f15b5066fbc1e03e6f27b3 100644
--- a/include/gpu/gl/SkMesaGLContext.h
+++ b/include/gpu/gl/SkMesaGLContext.h
@@ -8,11 +8,11 @@
 #ifndef SkMesaGLContext_DEFINED
 #define SkMesaGLContext_DEFINED
 
-#include "SkGLContext.h"
+#include "SkGLContextHelper.h"
 
 #if SK_MESA
 
-class SkMesaGLContext : public SkGLContext {
+class SkMesaGLContext : public SkGLContextHelper {
 private:
     typedef intptr_t Context;
 
@@ -23,6 +23,19 @@
 
     virtual void makeCurrent() const SK_OVERRIDE;
     virtual void swapBuffers() const SK_OVERRIDE;
+
+    class AutoContextRestore {
+    public:
+        AutoContextRestore();
+        ~AutoContextRestore();
+
+    private:
+        Context fOldContext;
+        GrGLint fOldWidth;
+        GrGLint fOldHeight;
+        GrGLint fOldFormat;
+        void*   fOldImage;
+    };
 
 protected:
     virtual const GrGLInterface* createGLContext(GrGLStandard forcedGpuAPI) SK_OVERRIDE;