Add offset to memory allocations

src/gpu/vk/GrVkMemory.h

 /*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #ifndef GrVkMemory_DEFINED
 #define GrVkMemory_DEFINED
 
 #include "vk/GrVkDefines.h"
+#include "vk/GrVkTypes.h"
 
 class GrVkGpu;
 
 namespace GrVkMemory {
     /**
     * Allocates vulkan device memory and binds it to the gpu's device for the given object.
     * Returns true of allocation succeeded.
     */
     bool AllocAndBindBufferMemory(const GrVkGpu* gpu,
                                   VkBuffer buffer,
                                   const VkMemoryPropertyFlags flags,
-                                  VkDeviceMemory* memory);
+                                  GrVkAlloc* alloc);
+    void FreeBufferMemory(const GrVkGpu* gpu, const GrVkAlloc& alloc);
 
     bool AllocAndBindImageMemory(const GrVkGpu* gpu,
                                  VkImage image,
                                  const VkMemoryPropertyFlags flags,
-                                 VkDeviceMemory* memory);
+                                 GrVkAlloc* alloc);
+    void FreeImageMemory(const GrVkGpu* gpu, const GrVkAlloc& alloc);
 
     VkPipelineStageFlags LayoutToPipelineStageFlags(const VkImageLayout layout);
 
     VkAccessFlags LayoutToSrcAccessMask(const VkImageLayout layout);
 }
 
 #endif