Vulkan: Don't create zero-sized textures.

Make sure the old resources are deleted but do not create new resources.

BUG=angleproject:2161

Change-Id: Ia6685e5c67b160d9bcd503983aee9607b2bd402c
Reviewed-on: https://chromium-review.googlesource.com/891644
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/RenderTargetVk.cpp b/src/libANGLE/renderer/vulkan/RenderTargetVk.cpp
index b559320..8098bff 100644
--- a/src/libANGLE/renderer/vulkan/RenderTargetVk.cpp
+++ b/src/libANGLE/renderer/vulkan/RenderTargetVk.cpp
@@ -13,13 +13,18 @@
 {
 
 RenderTargetVk::RenderTargetVk()
-    : format(nullptr),
-      image(nullptr),
-      imageView(nullptr),
-      extents(),
-      samples(VK_SAMPLE_COUNT_1_BIT),
-      resource(nullptr)
 {
+    reset();
+}
+
+void RenderTargetVk::reset()
+{
+    format    = nullptr;
+    image     = nullptr;
+    imageView = nullptr;
+    extents   = gl::Extents();
+    samples   = VK_SAMPLE_COUNT_1_BIT;
+    resource  = nullptr;
 }
 
 }  // namespace rx