Reland of MSE: Verify MediaLog events created by existing MP4 unit tests

Reland of MSE: Verify MediaLog events created by existing MP4 unit tests (patchset #1 id:1 of https://codereview.chromium.org/1306783003/ )

Reason for revert:
Relanding this now that the fixed prerequisite CL (https://codereview.chromium.org/1306923004/) has landed.

Original issue's description:
> Revert of MSE: Verify MediaLog events created by existing MP4 unit tests (patchset #2 id:20001 of https://codereview.chromium.org/1300013002/ )
>
> Reason for revert:
> Prerequisite CL (https://codereview.chromium.org/1300943002/) is breaking windows bots (http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/41148), so reverting both this and it to unblock tree.
>
> Original issue's description:
> > MSE: Verify MediaLog events created by existing MP4 unit tests
> >
> > Similar to previous changes r342861 and
> > https://codereview.chromium.org/1300943002/, this change updates media
> > unit tests to provide a StrictMock<MockMediaLog> to verify MediaLog
> > events produced with existing MSE MP4 unit tests. While log message
> > maintenance burden is increased, helpers are used to reduce that burden
> > while gaining improved resilience against logging regression.
> >
> > This CL does not verify all possible MSE MP4 parser MEDIA_LOGs, just
> > those that are emitted by existing unit tests.
> >
> > TEST=no regression
> >
> > Committed: https://crrev.com/194a2651ece516dc91fa0da9aa1675afd307e36e
> > Cr-Commit-Position: refs/heads/master@{#345183}
>
> TBR=xhwang@chromium.org,chcunningham@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
>
> Committed: https://crrev.com/61053d4768697c51bad15d7a9bdffa98c591bb7e
> Cr-Commit-Position: refs/heads/master@{#345205}

TBR=xhwang@chromium.org,chcunningham@chromium.org
BUG=524597
Committed: https://crrev.com/e36716b881725c20eb593b4151341f1053400bf2
Cr-Commit-Position: refs/heads/master@{#345775}

[wolenetz, 2015-08-27 02:09:11]

Created Reland of MSE: Verify MediaLog events created by existing MP4 unit tests

[commit-bot: I haz the power, 2015-08-27 02:09:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1317063003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1317063003/1

[wolenetz, 2015-08-27 02:09:39]

The CQ bit was unchecked by wolenetz@chromium.org

[commit-bot: I haz the power, 2015-08-27 02:10:07]

The CQ bit was unchecked by commit-bot@chromium.org

[wolenetz, 2015-08-27 02:13:33]

The CQ bit was checked by wolenetz@chromium.org

[commit-bot: I haz the power, 2015-08-27 02:14:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1317063003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1317063003/1

[commit-bot: I haz the power, 2015-08-27 02:44:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-27 02:45:02]

Patchset 1 (id:??) landed as
https://crrev.com/e36716b881725c20eb593b4151341f1053400bf2
Cr-Commit-Position: refs/heads/master@{#345775}