Handle the timeout exception when closing the dialog.

Sometimes the function failed to find the "close-button" because it's closed.
This can be due to a recent change in telemetry. See bug for more details.

Bug: 884929
Change-Id: I47af2f8e87431120d5dfebba3d25ead91d98f565
Reviewed-on: https://chromium-review.googlesource.com/1229359
Commit-Queue: Clifford Cheng <cliffordcheng@chromium.org>
Reviewed-by: Derek Cheng <imcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592532}

chrome/test/media_router/telemetry/benchmarks/pagesets/media_router_page.py

@@ -38,11 +38,14 @@ class CastPage(page.Page):
           'shadowRoot.getElementById("container-header").shadowRoot.' +
           'getElementById("close-button").click();')
     except (exceptions.DevtoolsTargetCrashException,
-            exceptions.EvaluateException):
+            exceptions.EvaluateException,
+            exceptions.TimeoutException):
       # Ignore the crash exception, this exception is caused by the js
       # code which closes the dialog, it is expected.
       # Ignore the evaluate exception, this exception maybe caused by the dialog
       # is closed/closing when the JS is executing.
+      # Ignore the timeout exception, this exception can be caused by finding
+      # the close-button on a dialog that is already closed.
       pass