Wait for CRD daemon process to be killed before returning.

Wait for CRD daemon process to be killed before returning.

This should mean that "/etc/init.d/chrome-remote-desktop restart" will
stop the service and won't try to start it again until the daemon is
killed.

A timeout is used to make sure that system shutdown is not paused
indefinitely if the daemon is unkillable.

Note that, since the daemon is not a child process, os.waitpid() cannot
be used for this. The psutil Python module is used instead. Some other
parts of the script have been updated as well to use psutil methods.
This is slightly safer, as psutil has some PID-reuse detection built in.

BUG=334437
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=278267

[Sergey Ulanov, 2014-06-18 00:23:58]

lgtm

https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
File remoting/host/linux/linux_me2me_host.py (right):

https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
remoting/host/linux/linux_me2me_host.py:984: if proc is not None:
nit: why not 'proc != None'?
Or I would prefer 'if proc:'

Same for all changes below

[Lambros, 2014-06-18 00:44:57]

https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
File remoting/host/linux/linux_me2me_host.py (right):

https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
remoting/host/linux/linux_me2me_host.py:984: if proc is not None:
On 2014/06/18 00:23:58, Sergey Ulanov wrote:
> nit: why not 'proc != None'?
> Or I would prefer 'if proc:'
> 
> Same for all changes below

I'm following the advice from the Google Python style guide here:
http://google-styleguide.googlecode.com/svn/trunk/pyguide.html?showone=True/F...

which says:
"Never use == or != to compare singletons like None. Use is or is not."

[Sergey Ulanov, 2014-06-18 08:01:28]

https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
File remoting/host/linux/linux_me2me_host.py (right):

https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
remoting/host/linux/linux_me2me_host.py:984: if proc is not None:
On 2014/06/18 00:44:57, Lambros wrote:
> On 2014/06/18 00:23:58, Sergey Ulanov wrote:
> > nit: why not 'proc != None'?
> > Or I would prefer 'if proc:'
> > 
> > Same for all changes below
> 
> I'm following the advice from the Google Python style guide here:
>
http://google-styleguide.googlecode.com/svn/trunk/pyguide.html?showone=True/F...
> 
> which says:
> "Never use == or != to compare singletons like None. Use is or is not."

I didn't know about this. Still, the guide says the following:
  Use the "implicit" false if at all possible, e.g., if foo: rather than if foo
!= []:. 

And I think that rule takes priority over not using != for None. So it's still
better to write this expression as "if proc:"

[Lambros, 2014-06-18 21:24:30]

On 2014/06/18 08:01:28, Sergey Ulanov wrote:
>
https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
> File remoting/host/linux/linux_me2me_host.py (right):
> 
>
https://codereview.chromium.org/335303002/diff/1/remoting/host/linux/linux_me...
> remoting/host/linux/linux_me2me_host.py:984: if proc is not None:
> On 2014/06/18 00:44:57, Lambros wrote:
> > On 2014/06/18 00:23:58, Sergey Ulanov wrote:
> > > nit: why not 'proc != None'?
> > > Or I would prefer 'if proc:'
> > > 
> > > Same for all changes below
> > 
> > I'm following the advice from the Google Python style guide here:
> >
>
http://google-styleguide.googlecode.com/svn/trunk/pyguide.html?showone=True/F...
> > 
> > which says:
> > "Never use == or != to compare singletons like None. Use is or is not."
> 
> I didn't know about this. Still, the guide says the following:
>   Use the "implicit" false if at all possible, e.g., if foo: rather than if
foo
> != []:. 
> 
> And I think that rule takes priority over not using != for None. So it's still
> better to write this expression as "if proc:"

The Google guide could be clearer, but using "is"/"is not" feels safer and more
correct, from everything I've read.

We have a method that returns some object (Process), or the singleton (None)
in case of process-not-found. So we want to test for that specific singleton.
We're not testing some kind of true/false property of the returned object
(which psutil may decide to implement one day). So I think the exception/caveat
applies, not the general rule. And all the style-guides I've seen say that
"is"/"is not" are the proper way in Python to test for None.

[Lambros, 2014-06-18 21:25:46]

The CQ bit was checked by lambroslambrou@chromium.org

[commit-bot: I haz the power, 2014-06-18 21:28:39]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/lambroslambrou@chromium.org/335303002/1

[commit-bot: I haz the power, 2014-06-19 04:16:44]

Change committed as 278267