Revert of Consolidate GPU buffer implementations

src/gpu/vk/GrVkTransferBuffer.h

Index: src/gpu/vk/GrVkTransferBuffer.h
diff --git a/src/gpu/vk/GrVkTransferBuffer.h b/src/gpu/vk/GrVkTransferBuffer.h
index c6ca2147b38b1caa08ceed5c7892bf4c25fef497..f978df95fd744cf7cc14138c35e1e544e96c5e24 100644
--- a/src/gpu/vk/GrVkTransferBuffer.h
+++ b/src/gpu/vk/GrVkTransferBuffer.h
@@ -8,13 +8,13 @@
 #ifndef GrVkTransferBuffer_DEFINED
 #define GrVkTransferBuffer_DEFINED
 
-#include "GrBuffer.h"
+#include "GrTransferBuffer.h"
 #include "GrVkBuffer.h"
 #include "vk/GrVkInterface.h"
 
 class GrVkGpu;
 
-class GrVkTransferBuffer : public GrBuffer, public GrVkBuffer {
+class GrVkTransferBuffer : public GrTransferBuffer, public GrVkBuffer {
 
 public:
     static GrVkTransferBuffer* Create(GrVkGpu* gpu, size_t size, GrVkBuffer::Type type);
@@ -29,9 +29,11 @@
     void setMemoryBacking(SkTraceMemoryDump* traceMemoryDump,
                           const SkString& dumpName) const override;
 
-    void onMap() override {
+    void* onMap() override {
         if (!this->wasDestroyed()) {
-            this->GrBuffer::fMapPtr = this->vkMap(this->getVkGpu());
+            return this->vkMap(this->getVkGpu());
+        } else {
+            return nullptr;
         }
     }
 
@@ -41,17 +43,12 @@
         }
     }
 
-    bool onUpdateData(const void* src, size_t srcSizeInBytes) override {
-        SkFAIL("Not implemented for transfer buffers.");
-        return false;
-    }
-
     GrVkGpu* getVkGpu() const {
         SkASSERT(!this->wasDestroyed());
         return reinterpret_cast<GrVkGpu*>(this->getGpu());
     }
 
-    typedef GrBuffer INHERITED;
+    typedef GrTransferBuffer INHERITED;
 };
 
 #endif