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..e58d5e40ff1bd6df21d3acff5de20fe7d52ab5df 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; }
@@ -83,8 +84,12 @@ protected:
         : fDesc(desc), fResource(resource), fOffset(0), fMapPtr(nullptr) {
     }
 
-    void* vkMap(const GrVkGpu* gpu);
-    void vkUnmap(GrVkGpu* gpu);
+    void* vkMap(GrVkGpu* gpu) {
+        this->internalMap(gpu, fDesc.fSizeInBytes);
+        return fMapPtr;
+    }
+    void vkUnmap(GrVkGpu* gpu) { this->internalUnmap(gpu, this->size()); }
+
     // 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.
     bool vkUpdateData(GrVkGpu* gpu, const void* src, size_t srcSizeInBytes,
@@ -99,6 +104,9 @@ private:
         return Create(gpu, descriptor);
     }
 
+    void internalMap(GrVkGpu* gpu, size_t size, bool* createdNewBuffer = nullptr);
+    void internalUnmap(GrVkGpu* gpu, size_t size);
+
     void validate() const;
     bool vkIsMapped() const;