Snow has a slow TPM and appears to be slow in general.

Some tests are failing on Snow because cryptohome doesn't unmount in time.
Attempting to increase this timeout to alleviate the issue.
We can revert this patch if it doesn't help.

BUG=449746
TEST=various telemetry-based autotests on Snow

Review URL: https://codereview.chromium.org/871923007

Cr-Commit-Position: refs/heads/master@{#313173}

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

@@ -156,7 +156,7 @@ class CrOSBrowserBackend(chrome_browser_backend.ChromeBrowserBackend):
       self._cri.RestartUI(False) # Logs out.
       self._cri.CloseConnection()
 
-    util.WaitFor(lambda: not self._IsCryptohomeMounted(), 30)
+    util.WaitFor(lambda: not self._IsCryptohomeMounted(), 180)
 
     if self._forwarder:
       self._forwarder.Close()