Fix telemetry extension profile generator for OSX.

Fix telemetry extension profile generator for OSX.

This CL includes several functionality fixes to the extension profile creator,
as well as several functionality improvements.
  - The URL to download extensions by identifier has changed, but the profile
  creator had not been updated.
  - Several of the extensions in many_extensions_profile_generator no longer
  exist, or no longer work.
  - There was a python error in _PrepareExtensionInstallFiles.
  - The old code waited 5 minutes for extensions to install. (And then waited
  for all tabs to load). The new code just waits 15 seconds, on the premise
  that it is better to fail fast than fail slow.
  - The old code required a clean installation of the OS, not connected to the
  corp network. The new code can be run from anywhere.

Caveat:
  - This CL removes the ability to generate an extension profile on Linux. This
  is not a functional change, since the previous code was already broken.

BUG=444230
Committed: https://crrev.com/300f7a40a8799dba69d39bfdc77f1d252b71ed0e
Cr-Commit-Position: refs/heads/master@{#311584}

[erikchen, 2015-01-09 19:48:37]

Patchset #1 (id:1) has been deleted

[erikchen, 2015-01-09 22:49:48]

Patchset #1 (id:20001) has been deleted

[erikchen, 2015-01-09 22:50:04]

erikchen@chromium.org changed reviewers:
+ dtu@chromium.org

[erikchen, 2015-01-09 22:50:04]

dtu: Please review.

[dtu, 2015-01-14 22:53:27]

lgtm

[erikchen, 2015-01-14 23:11:37]

The CQ bit was checked by erikchen@chromium.org

[commit-bot: I haz the power, 2015-01-14 23:12:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/847583002/40001

[commit-bot: I haz the power, 2015-01-15 00:20:36]

Committed patchset #1 (id:40001)

[commit-bot: I haz the power, 2015-01-15 00:22:31]

Patchset 1 (id:??) landed as
https://crrev.com/300f7a40a8799dba69d39bfdc77f1d252b71ed0e
Cr-Commit-Position: refs/heads/master@{#311584}