Add offset to memory allocations

include/gpu/vk/GrVkTypes.h

Index: include/gpu/vk/GrVkTypes.h
diff --git a/include/gpu/vk/GrVkTypes.h b/include/gpu/vk/GrVkTypes.h
index 94b765f668329c6f99922bb1c7c3de1c1674562b..f7351f8cf0607efe6fb59a175ca2cbb489571c79 100644
--- a/include/gpu/vk/GrVkTypes.h
+++ b/include/gpu/vk/GrVkTypes.h
@@ -36,6 +36,7 @@ struct GrVkImageInfo {
      */
     VkImage        fImage;
     VkDeviceMemory fAlloc;    // can be VK_NULL_HANDLE iff Tex is an RT and uses borrow semantics
+    VkDeviceSize   fOffset;
     VkImageTiling  fImageTiling;
     VkImageLayout  fImageLayout;
     VkFormat       fFormat;