Vulkan: Only re-create pipeline on state change.

This speeds up the simple perf test, but it is a very simple
optimization that does not have a cache of pipelines or anything
sophisticated.

BUG=angleproject:1898

Change-Id: Iec126bc73bf28f8bb33662a2f70670588f010d72
Reviewed-on: https://chromium-review.googlesource.com/444850
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/ProgramVk.cpp b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
index b0a06dd..6e53883 100644
--- a/src/libANGLE/renderer/vulkan/ProgramVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
@@ -108,6 +108,9 @@
     mLinkedVertexModule.retain(device, std::move(vertexModule));
     mLinkedFragmentModule.retain(device, std::move(fragmentModule));
 
+    // TODO(jmadill): Use pipeline cache.
+    context->invalidateCurrentPipeline();
+
     return true;
 }