Revert of MSE: Verify MediaLog events created by existing WebM unit tests

Revert of MSE: Verify MediaLog events created by existing WebM unit tests (patchset #3 id:40001 of https://codereview.chromium.org/1300943002/ )

Reason for revert:
This is breaking windows bots (http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/41148).

Original issue's description:
> MSE: Verify MediaLog events created by existing WebM unit tests
>
> Similar to previous SourceBufferStreamTests update in r342861, this
> change updates media unit tests to provide a StrictMock<MockMediaLog> to
> verify MediaLog events produced with existing MSE WebM unit tests. While
> log message maintenance burden is increased, helpers are included to
> reduce that burden while gaining improved resilience against logging
> regression.
>
> This CL does not verify all possible MSE WebM parser MEDIA_LOGs, just
> those that are emitted by existing unit tests.
>
> TEST=no regression
>
> Committed: https://crrev.com/b48815ca35b565e6ca372640ac25f79ee1a84c7e
> Cr-Commit-Position: refs/heads/master@{#345181}

TBR=xhwang@chromium.org,chcunningham@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/57f068f83e605fe5493f2785e3769162f4cd713e
Cr-Commit-Position: refs/heads/master@{#345206}

[wolenetz, 2015-08-24 23:37:03]

Created Revert of MSE: Verify MediaLog events created by existing WebM unit
tests

[commit-bot: I haz the power, 2015-08-24 23:37:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1310423003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1310423003/1

[commit-bot: I haz the power, 2015-08-24 23:38:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-24 23:39:09]

Patchset 1 (id:??) landed as
https://crrev.com/57f068f83e605fe5493f2785e3769162f4cd713e
Cr-Commit-Position: refs/heads/master@{#345206}

[wolenetz, 2015-08-25 19:21:51]

On 2015/08/24 23:39:09, commit-bot: I haz the power wrote:
> Patchset 1 (id:??) landed as
> https://crrev.com/57f068f83e605fe5493f2785e3769162f4cd713e
> Cr-Commit-Position: refs/heads/master@{#345206}

Reland attempt of a fixed version of the original CL is at
https://codereview.chromium.org/1306923004/