Correct typo in HangWatcher finch params

The IO thread param was used twice instead of the UI thread one.

Bug: 1034046
Change-Id: I06abd5f50760cd5b02ac53125a5f35b722ce2a0d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2363805
Auto-Submit: Oliver Li <olivierli@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#799665}

base/threading/hang_watcher.cc

@@ -227,7 +227,7 @@ bool HangWatcher::IsIOThreadHangWatchingEnabled() {
 }
 
 bool HangWatcher::IsUIThreadHangWatchingEnabled() {
-  return g_hang_watch_io_thread.load(std::memory_order_relaxed);
+  return g_hang_watch_ui_thread.load(std::memory_order_relaxed);
 }
 
 HangWatcher::HangWatcher()