Revert of Move GPU fences into sk_gpu_test

tools/gpu/gl/GLTestContext.h

Index: tools/gpu/gl/GLTestContext.h
diff --git a/tools/gpu/gl/GLTestContext.h b/tools/gpu/gl/GLTestContext.h
index 0cd9762f8bd5b148a8ffb3d14e2871f657624168..efe9d8f100f7f36f9792ad26f1a83fd9fece5763 100644
--- a/tools/gpu/gl/GLTestContext.h
+++ b/tools/gpu/gl/GLTestContext.h
@@ -59,38 +59,26 @@
      */
     virtual GLTestContext *createNew() const { return nullptr; }
 
-    template<typename Ret, typename... Args>
-    void getGLProcAddress(Ret(GR_GL_FUNCTION_TYPE** out)(Args...),
-                          const char* name, const char* ext = nullptr) const {
-        using Proc = Ret(GR_GL_FUNCTION_TYPE*)(Args...);
-        if (!SkStrStartsWith(name, "gl")) {
-            SkFAIL("getGLProcAddress: proc name must have 'gl' prefix");
-            *out = nullptr;
-        } else if (ext) {
-            SkString fullname(name);
-            fullname.append(ext);
-            *out = reinterpret_cast<Proc>(this->onPlatformGetProcAddress(fullname.c_str()));
-        } else {
-            *out = reinterpret_cast<Proc>(this->onPlatformGetProcAddress(name));
-        }
-    }
-
 protected:
     GLTestContext();
 
     /*
      * Methods that sublcasses must call from their constructors and destructors.
      */
-    void init(const GrGLInterface *, FenceSync* = nullptr);
+    void init(const GrGLInterface *, SkGpuFenceSync * = NULL);
 
     void teardown() override;
 
     virtual GrGLFuncPtr onPlatformGetProcAddress(const char *) const = 0;
 
 private:
+    class GLFenceSync;  // SkGpuFenceSync implementation that uses the OpenGL functionality.
+
     /** Subclass provides the gl interface object if construction was
      *  successful. */
     SkAutoTUnref<const GrGLInterface> fGL;
+
+    friend class GLFenceSync;  // For onPlatformGetProcAddress.
 
     typedef TestContext INHERITED;
 };