Implement Vulkan GrBackendObject for textures.

src/gpu/vk/GrVkTextureRenderTarget.cpp

Index: src/gpu/vk/GrVkTextureRenderTarget.cpp
diff --git a/src/gpu/vk/GrVkTextureRenderTarget.cpp b/src/gpu/vk/GrVkTextureRenderTarget.cpp
index 79ba90481eb075e82746fc781d9b876beb74aae2..241507473604ba1d29e7fe4170dd6c62fb323b44 100644
--- a/src/gpu/vk/GrVkTextureRenderTarget.cpp
+++ b/src/gpu/vk/GrVkTextureRenderTarget.cpp
@@ -12,6 +12,8 @@
 #include "GrVkImageView.h"
 #include "GrVkUtil.h"
 
+#include "vk/GrVkTypes.h"
+
 #define VK_CALL(GPU, X) GR_VK_CALL(GPU->vkInterface(), X)
 
 GrVkTextureRenderTarget*
@@ -140,11 +142,26 @@ GrVkTextureRenderTarget::CreateWrappedTextureRenderTarget(GrVkGpu* gpu,
                                                           const GrSurfaceDesc& desc,
                                                           GrGpuResource::LifeCycle lifeCycle,
                                                           VkFormat format, 
-                                                          GrVkImage::Resource* imageRsrc) {
-    SkASSERT(imageRsrc);
+                                                          const GrVkTextureInfo* info) {
+    // We can wrap a rendertarget without its allocation, as long as we don't take ownership
+    SkASSERT(info->fAlloc || kAdopted_LifeCycle != lifeCycle);
+
+    GrVkImage::Resource::Flags flags = (VK_IMAGE_TILING_LINEAR == info->fImageTiling)
+                                     ? Resource::kLinearTiling_Flag : Resource::kNo_Flags;
+
+    const GrVkImage::Resource* imageResource = new GrVkImage::Resource(info->fImage,
+                                                                       info->fAlloc,
+                                                                       flags);
+    if (!imageResource) {
+        return nullptr;
+    }
+
+    GrVkTextureRenderTarget* trt = GrVkTextureRenderTarget::Create(gpu, desc, lifeCycle,
+                                                                   format, imageResource);
+    // Create() will increment the refCount of the image resource if it succeeds
+    imageResource->unref(gpu);
+
+    return trt;
 
-    // Note: we assume the caller will unref the imageResource
-    // Create() will increment the refCount, and we'll unref when we're done with it
-    return GrVkTextureRenderTarget::Create(gpu, desc, lifeCycle, format, imageRsrc);
 }