Implement various vulkan stencil clears and fix various stenciling bugs.

src/gpu/vk/GrVkCommandBuffer.h

Index: src/gpu/vk/GrVkCommandBuffer.h
diff --git a/src/gpu/vk/GrVkCommandBuffer.h b/src/gpu/vk/GrVkCommandBuffer.h
index 33867abc5acc23c09af4087c17393ed5f26d8974..5cdb2c0b2f7cd6b4173c56416d0fd6b9632f1ba6 100644
--- a/src/gpu/vk/GrVkCommandBuffer.h
+++ b/src/gpu/vk/GrVkCommandBuffer.h
@@ -114,6 +114,12 @@ public:
                          uint32_t subRangeCount,
                          const VkImageSubresourceRange* subRanges);
 
+    void clearDepthStencilImage(const GrVkGpu* gpu,
+                                GrVkImage* image,
+                                const VkClearDepthStencilValue* color,
+                                uint32_t subRangeCount,
+                                const VkImageSubresourceRange* subRanges);
+
     void copyImage(const GrVkGpu* gpu,
                    GrVkImage* srcImage,
                    VkImageLayout srcLayout,