This is always the single variable declared in the catch scope.

BUG=

Change-Id: I05ccc48f57394268432c9b5b8c76f9db1b3b6312
Reviewed-on: https://chromium-review.googlesource.com/448041Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43571}