Revert of ChannelMojo: Let MessagePipeReader wait "peer closed" signal as well.

Revert of ChannelMojo: Let MessagePipeReader wait "peer closed" signal as well. (patchset #2 id:20001 of https://codereview.chromium.org/1023043002/)

Reason for revert:
speculative revert for "Too many open files" on various Mac bots.
e.g. http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac10.9/builds/17511/steps/webkit_tests/logs/stdio

Original issue's description:
> ChannelMojo: Let MessagePipeReader wait "peer closed" signal as well.
>
> This CL adds MOJO_SIGNAL_PEER_CLOSED for the MessagePipeReader's
> waiting bits. Without this, PRECONDITION_FAILED error can be notified
> at the end of the channel lifetime, and the browser process misinterprets
> it as a renderer crash, which results sadface screen.
>
> This rarely happens and is reproduced only with some underpowered CPU
> with excessive pressure. So we cannot have any reliable test.
>
> BUG=466814
> R=viettrungluu@chromium.org
>
> Committed: https://crrev.com/29d88220e88d21deaf6856b7ded300fa06ab94d3
> Cr-Commit-Position: refs/heads/master@{#322094}

TBR=viettrungluu@chromium.org,morrita@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=466814
Committed: https://crrev.com/5eab51f762a444966a1914cd15de196ee0d801a9
Cr-Commit-Position: refs/heads/master@{#322112}

[tkent, 2015-03-25 04:38:38]

Created Revert of ChannelMojo: Let MessagePipeReader wait "peer closed" signal
as well.

[commit-bot: I haz the power, 2015-03-25 04:39:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1035633002/1

[commit-bot: I haz the power, 2015-03-25 04:40:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-25 04:41:10]

Patchset 1 (id:??) landed as
https://crrev.com/5eab51f762a444966a1914cd15de196ee0d801a9
Cr-Commit-Position: refs/heads/master@{#322112}