Vulkan: Add vk::GetImpl helper.

Using reflection helpers, we can avoid having to pass the return
type to the GetImpl method.

BUG=angleproject:2200

Change-Id: Id160fbdf0ea8b3de2f219d3cc92394c678189a48
Reviewed-on: https://chromium-review.googlesource.com/742371
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/TextureVk.cpp b/src/libANGLE/renderer/vulkan/TextureVk.cpp
index 0b15df5..9553972 100644
--- a/src/libANGLE/renderer/vulkan/TextureVk.cpp
+++ b/src/libANGLE/renderer/vulkan/TextureVk.cpp
@@ -28,7 +28,7 @@
 
 gl::Error TextureVk::onDestroy(const gl::Context *context)
 {
-    ContextVk *contextVk = GetImplAs<ContextVk>(context);
+    ContextVk *contextVk = vk::GetImpl(context);
     RendererVk *renderer = contextVk->getRenderer();
 
     renderer->releaseResource(*this, &mImage);
@@ -49,7 +49,7 @@
                               const gl::PixelUnpackState &unpack,
                               const uint8_t *pixels)
 {
-    ContextVk *contextVk = GetImplAs<ContextVk>(context);
+    ContextVk *contextVk = vk::GetImpl(context);
     RendererVk *renderer = contextVk->getRenderer();
 
     // TODO(jmadill): support multi-level textures.