Store null GL context's state in interface object

include/gpu/gl/SkNullGLContext.h

Index: include/gpu/gl/SkNullGLContext.h
diff --git a/include/gpu/gl/SkNullGLContext.h b/include/gpu/gl/SkNullGLContext.h
index 9e799a9fea4d9d7b9b832026f4c664aee7a797ec..5a2a73fd8f54d73dbdbb8e25beda5a5becf04221 100644
--- a/include/gpu/gl/SkNullGLContext.h
+++ b/include/gpu/gl/SkNullGLContext.h
@@ -13,24 +13,14 @@
 class SK_API SkNullGLContext : public SkGLContext {
 public:
     ~SkNullGLContext() override;
-
     static SkNullGLContext* Create();
-    // FIXME: remove once Chromium has been updated.
-    static SkNullGLContext* Create(GrGLStandard forcedAPI) {
-        SkASSERT(forcedAPI == kNone_GrGLStandard);
-        (void)forcedAPI;        return Create();
-    }
-
-    class ContextState;
 
 private:
     SkNullGLContext();
 
-    void onPlatformMakeCurrent() const override;
+    void onPlatformMakeCurrent() const override {};
     void onPlatformSwapBuffers() const override {}
-    GrGLFuncPtr onPlatformGetProcAddress(const char*) const override { return NULL; }
-
-    ContextState* fState;
+    GrGLFuncPtr onPlatformGetProcAddress(const char*) const override { return nullptr; }
 };
 
 #endif