Vulkan: Move image layout into helper.

Now that we're using the helper everywhere, we can clean up the
vk::Image class and move the layout tracking into ImageHelper.

Bug: angleproject:2318
Change-Id: I9636835a2a3a76f181dac629bd4182bc5815cdee
Reviewed-on: https://chromium-review.googlesource.com/980774
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/ProgramVk.cpp b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
index 6287c93..c3d7367 100644
--- a/src/libANGLE/renderer/vulkan/ProgramVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
@@ -870,7 +870,7 @@
     const gl::State &glState     = contextVk->getGLState();
     const auto &completeTextures = glState.getCompleteTextureCache();
 
-    for (const auto &samplerBinding : mState.getSamplerBindings())
+    for (const gl::SamplerBinding &samplerBinding : mState.getSamplerBindings())
     {
         ASSERT(!samplerBinding.unreferenced);
 
@@ -884,7 +884,7 @@
         ASSERT(texture);
 
         TextureVk *textureVk   = vk::GetImpl(texture);
-        const vk::Image &image = textureVk->getImage();
+        const vk::ImageHelper &image = textureVk->getImage();
 
         VkDescriptorImageInfo &imageInfo = descriptorImageInfo[imageCount];