Refactor vulkan buffer mapping and unmapping

src/gpu/vk/GrVkBuffer.h

Index: src/gpu/vk/GrVkBuffer.h
diff --git a/src/gpu/vk/GrVkBuffer.h b/src/gpu/vk/GrVkBuffer.h
index 473a837646efcb6a5ebcabdd2224d76ab26244e9..a3028235425c443e4d259ebd9d9e25a7ce552f84 100644
--- a/src/gpu/vk/GrVkBuffer.h
+++ b/src/gpu/vk/GrVkBuffer.h
@@ -23,6 +23,7 @@ public:
     virtual ~GrVkBuffer() {
         // either release or abandon should have been called by the owner of this object.
         SkASSERT(!fResource);
+        delete [] (unsigned char*)fMapPtr;
     }
 
     VkBuffer                    buffer() const { return fResource->fBuffer; }
@@ -83,7 +84,7 @@ protected:
         : fDesc(desc), fResource(resource), fOffset(0), fMapPtr(nullptr) {
     }
 
-    void* vkMap(const GrVkGpu* gpu);
+    void* vkMap(GrVkGpu* gpu);
     void vkUnmap(GrVkGpu* gpu);
     // If the caller passes in a non null createdNewBuffer, this function will set the bool to true
     // if it creates a new VkBuffer to upload the data to.
@@ -99,6 +100,9 @@ private:
         return Create(gpu, descriptor);
     }
 
+    void innerMap(GrVkGpu* gpu, size_t size, bool* createdNewBuffer = nullptr);
+    void innerUnmap(GrVkGpu* gpu, size_t size);
+
     void validate() const;
     bool vkIsMapped() const;