Declare 20 renderer services on Android.

Declare 20 renderer services on Android.

On Android the OS manages Chrome's renderers on the system process list,
killing them under memory pressure and (as per KitKat) allowing a hard
maximum of 8 renderers in background.

As we're going to stop limiting the number of process hosts (and sharing
renderers among unrelated tabs) on Android, we want to have more
renderer services declared so that we don't run out of them when the OS
is particularly generous. According to UMA, we're at the current limit
at 1% of page loads.

This patch declares additional renderer services on Android, totalling 20
with the patch. After the embedders update, we will raise the actual limit
in ChildProcessLauncher in the next patch.

BUG=325842
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281324

[nasko, 2014-06-26 16:51:44]

If we are adjusting, might as well adjust it to have a comfortable margin. Based
on some analysis we did back in 2013Q1, worst case offenders in usage of iframes
were going to result in 15 processes. I'd suggest using 32, just to be on the
safe side and be able to test with full isolation enabled.

[klobag.chromium, 2014-06-28 01:44:35]

lgtm

20 is already a lot. Declare the service doesn't mean the platform will keep
them running.

[ppi, 2014-07-01 10:48:44]

+Yaron for OWNER look.

[Yaron, 2014-07-01 16:34:48]

lgtm

(of course you'll need an internal change too)

[ppi, 2014-07-03 12:54:21]

Thanks!

Yup. I think it would make sense to do a 3-way patch here - I'll keep the limit
at 13 in this one and raise it to 20 once the embedder-side lands.

[ppi, 2014-07-03 12:54:25]

The CQ bit was checked by ppi@chromium.org

[commit-bot: I haz the power, 2014-07-03 12:55:24]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ppi@chromium.org/356043002/40001

[commit-bot: I haz the power, 2014-07-03 21:11:13]

Change committed as 281324