Don't call SetPriorityClass when process_ is 0.

Don't call SetPriorityClass when process_ is 0.

BUG=15606

[tyoshino-do-not-use, 2009-07-06 14:50:52]

Hi Brett,

I've been trying to fix this crash.

http://crash/search?query=RenderWidgetHostViewWin::WasHidden+version:3.0

I investigated the source code and then mini dump attached to crash report. It
seems that the failing point is inside BrowserRenderProcessHost::SetBackgrounded
because the top of call trace is "call BrowserRenderProcessHost::SetBackgrounded
+ 0x0". But there're only jmp instruction to move inside the function and call
instructions in BrowserRenderProcessHost::SetBackgrounded's assembly. I couldn't
identify the cause why PC leaped 0x4000. Maybe stack is broken somewhere.

I'm not sure this patch make any improvement, but passing 0 to SetPriorityClass
looks not good. Let me change this for the meantime.

[brettw, 2009-07-06 14:59:51]

I think this patch is a good idea because most of the other functions in that
class do the check for process before continuing. I would add the same check in
IsProcessBackgrounded (maybe return false in that case).

I would probably not DCHECK in either of the two functions, since the other
functions in that class don't. We should really have a consistent story about
whether the caller should verify the process is valid before using it or not.

[tyoshino-do-not-use, 2009-07-06 17:01:34]

Thank you.

On 2009/07/06 14:59:51, brettw wrote:
> I think this patch is a good idea because most of the other functions in that
> class do the check for process before continuing. I would add the same check
in
> IsProcessBackgrounded (maybe return false in that case).
> 

OK. Added if-clause to IsProcessBackgrounded, too.

> I would probably not DCHECK in either of the two functions, since the other
> functions in that class don't. We should really have a consistent story about
> whether the caller should verify the process is valid before using it or not.

Removed. NOTREACHED and DCHECK.

Now try-ing

http://build.chromium.org/buildbot/try-server/builders/win/builds/8690
http://build.chromium.org/buildbot/try-server/builders/mac/builds/8144
http://build.chromium.org/buildbot/try-server/builders/linux/builds/8163

[brettw, 2009-07-06 17:03:24]

LGTM

[tyoshino-do-not-use, 2009-07-16 03:54:51]

On 2009/07/06 17:03:24, brettw wrote:
> LGTM

Thank you. Landed by myself. r20851