Fix vulkan build on linux and android

src/gpu/vk/GrVkGpu.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 GrVkGpu_DEFINED
 #define GrVkGpu_DEFINED
 
@@ skipping 55 matching lines @@
     void discard(GrRenderTarget*) override {}
 
     bool onCopySurface(GrSurface* dst,
                        GrSurface* src,
                        const SkIRect& srcRect,
                        const SkIPoint& dstPoint) override;
 
     void onGetMultisampleSpecs(GrRenderTarget* rt,
                                const GrStencilSettings&,
                                int* effectiveSampleCnt,
-                               SkAutoTDeleteArray<SkPoint>*);
+                               SkAutoTDeleteArray<SkPoint>*) override;
 
     bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const override;
 
     void xferBarrier(GrRenderTarget*, GrXferBarrierType) override {}
 
     GrBackendObject createTestingOnlyBackendTexture(void* pixels, int w, int h,
                                                     GrPixelConfig config) override;
     bool isTestingOnlyBackendTexture(GrBackendObject id) const override;
     void deleteTestingOnlyBackendTexture(GrBackendObject id, bool abandonTexture) override;
 
@@ skipping 134 matching lines @@
 
     // Shaderc compiler used for compiling glsl in spirv. We only want to create the compiler once
     // since there is significant overhead to the first compile of any compiler.
     shaderc_compiler_t fCompiler;
 
 
     typedef GrGpu INHERITED;
 };
 
 #endif