Push API: Avoid false positive DCHECK.

Push API: Avoid false positive DCHECK.

PushMessagingAppIdentifier::FindByAppId was DCHECKing when called from
PushMessagingServiceImpl::CanHandle to see if an app_id belongs to
Push, since it assumes that it would only be called with valid Push
app_ids.

This patch makes it test whether the app_id is a Push Messaging app_id
before performing any validation DCHECKs.

BUG=489304
Committed: https://crrev.com/c85006f042cf657a2e45b0b2fec5d32fedb67dff
Cr-Commit-Position: refs/heads/master@{#330378}

[johnme, 2015-05-18 15:51:07]

johnme@chromium.org changed reviewers:
+ mvanouwerkerk@chromium.org

[Michael van Ouwerkerk, 2015-05-18 15:52:51]

lgtm thanks!

[Peter Beverloo, 2015-05-18 16:05:39]

peter@chromium.org changed reviewers:
+ peter@chromium.org

[Peter Beverloo, 2015-05-18 16:05:40]

test?

[johnme, 2015-05-18 16:18:56]

Added test.

On 2015/05/18 16:05:40, Peter Beverloo wrote:
> test?

Done.

[Peter Beverloo, 2015-05-18 16:20:20]

lgtm, thanks! :)

[johnme, 2015-05-18 16:20:52]

The CQ bit was checked by johnme@chromium.org

[johnme, 2015-05-18 16:20:53]

The patchset sent to the CQ was uploaded after l-g-t-m from
mvanouwerkerk@chromium.org
Link to the patchset: https://codereview.chromium.org/1140873005/#ps20001
(title: "Add test")

[commit-bot: I haz the power, 2015-05-18 16:21:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1140873005/20001

[commit-bot: I haz the power, 2015-05-18 17:17:44]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-18 22:40:39]

Patchset 2 (id:??) landed as
https://crrev.com/c85006f042cf657a2e45b0b2fec5d32fedb67dff
Cr-Commit-Position: refs/heads/master@{#330378}