Catch TabCrashException that may occur as we poll for oobe disappearing.

We access oobe here as it is going away: https://code.google.com/p/chromium/codesearch#chromium/src/tools/telemetry/telemetry/core/backends/chrome/cros_browser_backend.py&q=oobe&l=343

BUG=chromium:332545
TEST=manual
NOTRY=True

Review URL: https://codereview.chromium.org/129343003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243690 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/telemetry/core/backends/chrome/misc_web_contents_backend.py

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 import json
 
+from telemetry.core import exceptions
 from telemetry.core import web_contents
 from telemetry.core.backends.chrome import inspector_backend
 
@@ -17,7 +18,10 @@ class MiscWebContentsBackend(object):
     if oobe_web_contents_info:
       debugger_url = oobe_web_contents_info.get('webSocketDebuggerUrl')
       if debugger_url:
-        inspector = self._CreateInspectorBackend(debugger_url)
+        try:
+          inspector = self._CreateInspectorBackend(debugger_url)
+        except exceptions.TabCrashException:
+          return None
         return web_contents.WebContents(inspector)
     return None