Implement various vulkan stencil clears and fix various stenciling bugs.

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 74 matching lines @@
 
     GrBackendObject createTestingOnlyBackendTexture(void* pixels, int w, int h,
                                                     GrPixelConfig config) override;
     bool isTestingOnlyBackendTexture(GrBackendObject id) const override;
     void deleteTestingOnlyBackendTexture(GrBackendObject id, bool abandonTexture) override;
 
     GrStencilAttachment* createStencilAttachmentForRenderTarget(const GrRenderTarget*,
                                                                 int width,
                                                                 int height) override;
 
-    void clearStencil(GrRenderTarget* target) override {
-        SkDebugf("clearStencil not yet implemented for Vulkan\n");
-    }
+    void clearStencil(GrRenderTarget* target) override;
 
     void drawDebugWireRect(GrRenderTarget*, const SkIRect&, GrColor) override {
         SkDebugf("drawDebugWireRect not yet implemented for Vulkan\n");
     }
 
     void addMemoryBarrier(VkPipelineStageFlags srcStageMask,
                           VkPipelineStageFlags dstStageMask,
                           bool byRegion,
                           VkMemoryBarrier* barrier) const;
     void addBufferMemoryBarrier(VkPipelineStageFlags srcStageMask,
@@ skipping 34 matching lines @@
         SkDebugf("onWrapBackendTextureAsRenderTarget not yet implemented for Vulkan\n");
         return NULL;
     }
 
     GrVertexBuffer* onCreateVertexBuffer(size_t size, bool dynamic) override;
     GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) override;
     GrTransferBuffer* onCreateTransferBuffer(size_t size, TransferType type) override;
 
     void onClear(GrRenderTarget*, const SkIRect& rect, GrColor color) override;
 
-    void onClearStencilClip(GrRenderTarget*, const SkIRect& rect, bool insideClip) override {
-        SkDebugf("onClearStencilClip not yet implemented for Vulkan\n");
-    }
+    void onClearStencilClip(GrRenderTarget*, const SkIRect& rect, bool insideClip) override;
 
     void onDraw(const DrawArgs&, const GrNonInstancedVertices&) override;
 
     bool onReadPixels(GrSurface* surface,
                       int left, int top, int width, int height,
                       GrPixelConfig,
                       void* buffer,
                       size_t rowBytes) override;
 
     bool onWritePixels(GrSurface* surface,
@@ skipping 51 matching lines @@
     shaderc_compiler_t fCompiler;
 
     // This is only for our current testing and building. The client should be holding on to the
     // VkInstance.
     VkInstance                        fVkInstance;
 
     typedef GrGpu INHERITED;
 };
 
 #endif