GL backend: Only synchronize transform feedback state when it changes.

BUG=angleproject:2188

Change-Id: I5bfcc038c887dde0770564d103eb3cb234b248c9
Reviewed-on: https://chromium-review.googlesource.com/794100
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/ContextVk.cpp b/src/libANGLE/renderer/vulkan/ContextVk.cpp
index 8b9dcc1..bf422e0 100644
--- a/src/libANGLE/renderer/vulkan/ContextVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ContextVk.cpp
@@ -709,6 +709,9 @@
             case gl::State::DIRTY_BIT_SAMPLER_BINDINGS:
                 dirtyTextures = true;
                 break;
+            case gl::State::DIRTY_BIT_TRANSFORM_FEEDBACK_BINDING:
+                WARN() << "DIRTY_BIT_TRANSFORM_FEEDBACK_BINDING unimplemented";
+                break;
             case gl::State::DIRTY_BIT_MULTISAMPLING:
                 WARN() << "DIRTY_BIT_MULTISAMPLING unimplemented";
                 break;