Vulkan: Fix cube map attachment clears and readpixels.

These were both missing the correct layer offset. Cache the layer
inside the RenderTargetVk for easy access.

Bug: angleproject:2470
Change-Id: I690dbf0702d7ec52f44ba0a9429b6ef0e51baf6b
Reviewed-on: https://chromium-review.googlesource.com/1225910
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/SurfaceVk.cpp b/src/libANGLE/renderer/vulkan/SurfaceVk.cpp
index 7a072de..e1a58d0 100644
--- a/src/libANGLE/renderer/vulkan/SurfaceVk.cpp
+++ b/src/libANGLE/renderer/vulkan/SurfaceVk.cpp
@@ -59,7 +59,7 @@
 }  // namespace
 
 OffscreenSurfaceVk::AttachmentImage::AttachmentImage(vk::CommandGraphResource *commandGraphResource)
-    : renderTarget(&image, &imageView, commandGraphResource)
+    : renderTarget(&image, &imageView, commandGraphResource, 0)
 {
 }
 
@@ -268,8 +268,8 @@
       mSurface(VK_NULL_HANDLE),
       mInstance(VK_NULL_HANDLE),
       mSwapchain(VK_NULL_HANDLE),
-      mColorRenderTarget(nullptr, nullptr, this),
-      mDepthStencilRenderTarget(&mDepthStencilImage, &mDepthStencilImageView, this),
+      mColorRenderTarget(nullptr, nullptr, this, 0),
+      mDepthStencilRenderTarget(&mDepthStencilImage, &mDepthStencilImageView, this, 0),
       mCurrentSwapchainImageIndex(0)
 {
 }