Implement various vulkan stencil clears and fix various stenciling bugs.

src/gpu/vk/GrVkRenderTarget.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrVkRenderTarget.h"
 
 #include "GrRenderTargetPriv.h"
@@ skipping 178 matching lines @@
     SkASSERT(imageDesc.fUsageFlags & VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT);
 
     const GrVkImage::Resource* imageResource = GrVkImage::CreateResource(gpu, imageDesc);
     if (!imageResource) {
         return nullptr;
     }
 
     GrVkRenderTarget* rt = GrVkRenderTarget::Create(gpu, desc, lifeCycle, imageResource);
     // Create() will increment the refCount of the image resource if it succeeds
     imageResource->unref(gpu);
-
     return rt;
 }
 
 GrVkRenderTarget*
 GrVkRenderTarget::CreateWrappedRenderTarget(GrVkGpu* gpu,
                                             const GrSurfaceDesc& desc,
                                             GrGpuResource::LifeCycle lifeCycle,
                                             const GrVkImage::Resource* imageResource) {
     SkASSERT(imageResource);
 
@@ skipping 172 matching lines @@
 
     return nullptr;
 }
 
 
 GrVkGpu* GrVkRenderTarget::getVkGpu() const {
     SkASSERT(!this->wasDestroyed());
     return static_cast<GrVkGpu*>(this->getGpu());
 }