Fix vulkan build

src/gpu/vk/GrVkUniformBuffer.h

 /*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #ifndef GrVkUniformBuffer_DEFINED
 #define GrVkUniformBuffer_DEFINED
 
@@ skipping 32 matching lines @@
         void onRecycle(GrVkGpu* gpu) const override;
 
         typedef GrVkBuffer::Resource INHERITED;
     };
 
     const GrVkBuffer::Resource* createResource(GrVkGpu* gpu,
                                                const GrVkBuffer::Desc& descriptor) override;
 
     GrVkUniformBuffer(GrVkGpu* gpu, const GrVkBuffer::Desc& desc,
                       const GrVkUniformBuffer::Resource* resource)
-        : INHERITED(desc, resource)
-        , fGpu(gpu) {}
-
-    GrVkGpu* fGpu;
+        : INHERITED(desc, resource) {}
 
     typedef GrVkBuffer INHERITED;
 };
 
 #endif