Use RecvMsgWithPid to find zygote PID instead of chrome-sandbox

Use RecvMsgWithPid to find zygote PID instead of chrome-sandbox

BUG=357670
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266618

[jln (very slow on Chromium), 2014-04-26 00:54:09]

lgtm, I'm very happy to see this moving!

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
File content/browser/zygote_host/zygote_host_impl_linux.cc (right):

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
content/browser/zygote_host/zygote_host_impl_linux.cc:51: // Returns true if
proc is the same process as or a descendent process of
nit: |proc| is the prevailing style in new code.
nit2: you called it |root| not |ancestor|

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
content/browser/zygote_host/zygote_host_impl_linux.cc:176: // Wait for the
zygote to tell us it's running, and receive its PID.
Do you want to add a longer comment here?

Let's explain that there is a PID namespace and that the kernel will
automatically translate the PID sent via the UnixDomainSocket().

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
content/browser/zygote_host/zygote_host_impl_linux.cc:192: "See
crbug.com/357670.";
Let's add a note that they can use "--" + kDisableSetuidSandbox to work around
this?

https://codereview.chromium.org/258893004/diff/1/content/zygote/zygote_main_l...
File content/zygote/zygote_main_linux.cc (right):

https://codereview.chromium.org/258893004/diff/1/content/zygote/zygote_main_l...
content/zygote/zygote_main_linux.cc:456: // We have no use for the zygote ID
descriptor anymore.
Maybe be more explicit? "kZygoteIdFd has been passed to US because of an ancient
setuid sandbox ABI requirement. It's a useless dummy, close it."

[mdempsky, 2014-04-26 03:07:14]

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
File content/browser/zygote_host/zygote_host_impl_linux.cc (right):

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
content/browser/zygote_host/zygote_host_impl_linux.cc:51: // Returns true if
proc is the same process as or a descendent process of
On 2014/04/26 00:54:10, jln wrote:
> nit: |proc| is the prevailing style in new code.
> nit2: you called it |root| not |ancestor|

Oops, done.

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
content/browser/zygote_host/zygote_host_impl_linux.cc:176: // Wait for the
zygote to tell us it's running, and receive its PID.
On 2014/04/26 00:54:10, jln wrote:
> Do you want to add a longer comment here?
> 
> Let's explain that there is a PID namespace and that the kernel will
> automatically translate the PID sent via the UnixDomainSocket().

Done.  PTAL and let me know if you think the new wording is clear enough.

https://codereview.chromium.org/258893004/diff/1/content/browser/zygote_host/...
content/browser/zygote_host/zygote_host_impl_linux.cc:192: "See
crbug.com/357670.";
On 2014/04/26 00:54:10, jln wrote:
> Let's add a note that they can use "--" + kDisableSetuidSandbox to work around
> this?

Done.

[mdempsky, 2014-04-26 06:05:58]

https://codereview.chromium.org/258893004/diff/1/content/zygote/zygote_main_l...
File content/zygote/zygote_main_linux.cc (right):

https://codereview.chromium.org/258893004/diff/1/content/zygote/zygote_main_l...
content/zygote/zygote_main_linux.cc:456: // We have no use for the zygote ID
descriptor anymore.
On 2014/04/26 00:54:10, jln wrote:
> Maybe be more explicit? "kZygoteIdFd has been passed to US because of an
ancient
> setuid sandbox ABI requirement. It's a useless dummy, close it."

Done.

[mdempsky, 2014-04-28 18:05:44]

The CQ bit was checked by mdempsky@chromium.org

[commit-bot: I haz the power, 2014-04-28 18:05:59]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mdempsky@chromium.org/258893004/20001

[commit-bot: I haz the power, 2014-04-28 18:31:50]

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

[commit-bot: I haz the power, 2014-04-28 18:31:50]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_chromeos_rel

[jln (very slow on Chromium), 2014-04-28 18:33:56]

The CQ bit was checked by jln@chromium.org

[commit-bot: I haz the power, 2014-04-28 18:35:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mdempsky@chromium.org/258893004/20001

[jln (very slow on Chromium), 2014-04-28 19:04:54]

The Linux bots have all passed. I'm going to NOTRY=true this change and closely
monitor the tree.

[jln (very slow on Chromium), 2014-04-28 19:05:06]

The CQ bit was unchecked by jln@chromium.org

[jln (very slow on Chromium), 2014-04-28 19:05:12]

The CQ bit was checked by jln@chromium.org

[commit-bot: I haz the power, 2014-04-28 19:05:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mdempsky@chromium.org/258893004/20001

[commit-bot: I haz the power, 2014-04-28 19:08:02]

Change committed as 266618