[TTS] Fix a crash recently introduced.

Protect against a null ContextualSearchManager when an Overlay
Panel is shown.  The ContextualSearchTabHelper needs to check
for a null CSM before asking if it is active. If there's no CSM
then we don't need to update the hooks even though it can't be active.

BUG=930615

Change-Id: I1fe106a29978a007d80e908590a40526b696a73f
Reviewed-on: https://chromium-review.googlesource.com/c/1465164
Commit-Queue: Donn Denman <donnd@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Auto-Submit: Donn Denman <donnd@chromium.org>
Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631019}
1 file changed