Fix device_event_log component build, make NonThreadSafe (Take 2)

Fix device_event_log component build, make NonThreadSafe (Take 2)

This patch includes the correct GN changes.

This CL does the following:
* Fixes the component build
* Limits the length of LogEntry strings
* Cleans up the code a little to help with crash debugging

BUG=479095
For device_event_log gypi:
TBR=reillyg@chromium.org

Committed: https://crrev.com/6a00a6f0a46ce2852dc526dfc2ea056a8115ef8c
Cr-Commit-Position: refs/heads/master@{#329320}

[stevenjb, 2015-05-12 01:11:31]

The CQ bit was checked by stevenjb@chromium.org

[commit-bot: I haz the power, 2015-05-12 01:13:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1140643002/1

[commit-bot: I haz the power, 2015-05-12 02:14:19]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-12 02:15:22]

Patchset 1 (id:??) landed as
https://crrev.com/6a00a6f0a46ce2852dc526dfc2ea056a8115ef8c
Cr-Commit-Position: refs/heads/master@{#329320}