Consolidate GPU buffer implementations

src/gpu/vk/GrVkIndexBuffer.cpp

Index: src/gpu/vk/GrVkIndexBuffer.cpp
diff --git a/src/gpu/vk/GrVkIndexBuffer.cpp b/src/gpu/vk/GrVkIndexBuffer.cpp
index 52f7bd59b738d37c90ebaeda00f8bd141fbd3b64..6cec856cd4d661161b9d8828b47c7e0947508fa8 100644
--- a/src/gpu/vk/GrVkIndexBuffer.cpp
+++ b/src/gpu/vk/GrVkIndexBuffer.cpp
@@ -10,7 +10,8 @@
 
 GrVkIndexBuffer::GrVkIndexBuffer(GrVkGpu* gpu, const GrVkBuffer::Desc& desc,
                                  const GrVkBuffer::Resource* bufferResource)
-    : INHERITED(gpu, desc.fSizeInBytes, desc.fDynamic, false)
+    : INHERITED(gpu, kIndex_GrBufferType, desc.fSizeInBytes,
+                desc.fDynamic ? kDynamic_GrAccessPattern : kStatic_GrAccessPattern, false)
     , GrVkBuffer(desc, bufferResource) {
     this->registerWithCache();
 }
@@ -47,11 +48,9 @@ void GrVkIndexBuffer::onAbandon() {
     INHERITED::onAbandon();
 }
 
-void* GrVkIndexBuffer::onMap() {
+void GrVkIndexBuffer::onMap() {
     if (!this->wasDestroyed()) {
-        return this->vkMap(this->getVkGpu());
-    } else {
-        return NULL;
+        this->GrBuffer::fMapPtr = this->vkMap(this->getVkGpu());
     }
 }