Use a better method to generate a random ID in IvfFileWriterTest.

Use a better method to generate a random ID in IvfFileWriterTest.

It was generating a random ID using the test case's "this" pointer
and the current time. However, the current time may be imprecise. And
the "this" pointer may have repeatable values.

BUG=webrtc:5898
Committed: https://crrev.com/55b0b3755421c7b795d78cf5836677078423a27f
Cr-Commit-Position: refs/heads/master@{#13560}

[Taylor Brandstetter, 2016-07-27 21:29:20]

deadbeef@webrtc.org changed reviewers:
+ stefan@webrtc.org

[stefan-webrtc, 2016-07-28 07:14:30]

stefan@webrtc.org changed reviewers:
+ sprang@webrtc.org

[stefan-webrtc, 2016-07-28 07:14:31]

sprang@ is a better reviewer for this.

[sprang_webrtc, 2016-07-28 11:51:52]

lgtm

[stefan-webrtc, 2016-07-28 12:27:55]

rs lgtm

[Taylor Brandstetter, 2016-07-28 16:46:38]

The CQ bit was checked by deadbeef@webrtc.org

[commit-bot: I haz the power, 2016-07-28 16:46:48]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2016-07-28 17:51:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-28 17:51:18]

Description was changed from

==========
Use a better method to generate a random ID in IvfFileWriterTest.

It was generating a random ID using the test case's "this" pointer
and the current time. However, the current time may be imprecise. And
the "this" pointer may have repeatable values.

BUG=webrtc:5898
==========

to

==========
Use a better method to generate a random ID in IvfFileWriterTest.

It was generating a random ID using the test case's "this" pointer
and the current time. However, the current time may be imprecise. And
the "this" pointer may have repeatable values.

BUG=webrtc:5898

Committed: https://crrev.com/55b0b3755421c7b795d78cf5836677078423a27f
Cr-Commit-Position: refs/heads/master@{#13560}
==========

[commit-bot: I haz the power, 2016-07-28 17:51:19]

Patchset 1 (id:??) landed as
https://crrev.com/55b0b3755421c7b795d78cf5836677078423a27f
Cr-Commit-Position: refs/heads/master@{#13560}