Revert of Consolidate GPU buffer implementations

src/gpu/vk/GrVkVertexBuffer.cpp

Index: src/gpu/vk/GrVkVertexBuffer.cpp
diff --git a/src/gpu/vk/GrVkVertexBuffer.cpp b/src/gpu/vk/GrVkVertexBuffer.cpp
index 1d3eadb42c87c5ff7e1fe4e37f3fb0341e2160cf..46c6d28f23d2bd7ec8b704635b7f814e58a98732 100644
--- a/src/gpu/vk/GrVkVertexBuffer.cpp
+++ b/src/gpu/vk/GrVkVertexBuffer.cpp
@@ -10,8 +10,7 @@
 
 GrVkVertexBuffer::GrVkVertexBuffer(GrVkGpu* gpu, const GrVkBuffer::Desc& desc,
                                    const GrVkBuffer::Resource* bufferResource)
-    : INHERITED(gpu, kVertex_GrBufferType, desc.fSizeInBytes,
-                desc.fDynamic ? kDynamic_GrAccessPattern : kStatic_GrAccessPattern, false)
+    : INHERITED(gpu, desc.fSizeInBytes, desc.fDynamic, false)
     , GrVkBuffer(desc, bufferResource) {
     this->registerWithCache();
 }
@@ -47,9 +46,11 @@
     INHERITED::onAbandon();
 }
 
-void GrVkVertexBuffer::onMap() {
+void* GrVkVertexBuffer::onMap() {
     if (!this->wasDestroyed()) {
-        this->GrBuffer::fMapPtr = this->vkMap(this->getVkGpu());
+        return this->vkMap(this->getVkGpu());
+    } else {
+        return NULL;
     }
 }