Fix the crash that happens if the default wallpaper image decoding failed.

Fix the crash that happens if the default wallpaper image decoding failed.

BUG=725667
Review-Url: https://codereview.chromium.org/2931063003
Cr-Commit-Position: refs/heads/master@{#479490}
Committed: https://chromium.googlesource.com/chromium/src/+/26f7ab8456c7e21751bd55ef1112a063dfc25203

[xdai1, 2017-06-09 18:30:30]

xdai@chromium.org changed reviewers:
+ bshe@chromium.org

[xdai1, 2017-06-09 18:30:32]

bshe@, could you help review this CL please? Thanks!

[xdai1, 2017-06-09 18:30:43]

The CQ bit was checked by xdai@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-06-09 18:31:09]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-09 19:05:27]

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

[commit-bot: I haz the power, 2017-06-09 19:05:28]

Dry run: This issue passed the CQ dry run.

[bshe, 2017-06-12 12:47:29]

On 2017/06/09 18:30:32, xdai1 wrote:
> bshe@, could you help review this CL please? Thanks!

hmm. How could a default wallpaper fail? And when it failed, what wallpaper do
we use?

[xdai1, 2017-06-14 17:54:54]

On 2017/06/12 12:47:29, bshe wrote:
> On 2017/06/09 18:30:32, xdai1 wrote:
> > bshe@, could you help review this CL please? Thanks!
> 
> hmm. How could a default wallpaper fail? And when it failed, what wallpaper do
> we use?

WallpaperManager::OnDefaultWallpaperDecoded() is the callback function of
user_image_loader::StartWithFilePath(). The function will be called regardless
of whether the load succeeds or not. Thus it's possible the |user_image| that we
get in WallpaperManager::OnDefaultWallpaperDecoded() is empty in case of error.
The call stack in the bug suggested that the crash was from here. 

If it fails, I think we don't use any other wallpaper... But since it was only
observed in the autotest desktopui_MusLogin, I think we should be fine?

[bshe, 2017-06-14 18:35:40]

On 2017/06/14 17:54:54, xdai1 wrote:
> On 2017/06/12 12:47:29, bshe wrote:
> > On 2017/06/09 18:30:32, xdai1 wrote:
> > > bshe@, could you help review this CL please? Thanks!
> > 
> > hmm. How could a default wallpaper fail? And when it failed, what wallpaper
do
> > we use?
> 
> WallpaperManager::OnDefaultWallpaperDecoded() is the callback function of
> user_image_loader::StartWithFilePath(). The function will be called regardless
> of whether the load succeeds or not. Thus it's possible the |user_image| that
we
> get in WallpaperManager::OnDefaultWallpaperDecoded() is empty in case of
error.
> The call stack in the bug suggested that the crash was from here. 
> 
> If it fails, I think we don't use any other wallpaper... But since it was only
> observed in the autotest desktopui_MusLogin, I think we should be fine?

It is the callback function of StartWithFilePath. But the file path should
always
point to a default wallpaper on the disk. I dont see how it could fail unless
the default wallpaper on the disk is somehow corrupted... It would be nice to
understand
why it failed but I understand this is not a priority since it only happens on a
test bot.
lgtm

[xdai1, 2017-06-14 19:59:07]

The CQ bit was checked by xdai@chromium.org

[commit-bot: I haz the power, 2017-06-14 19:59:41]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-14 20:33:32]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1497470347625160, "parent_rev":
"03c1f4449fec6a5fe7406647023b0c8b6531444a", "commit_rev":
"26f7ab8456c7e21751bd55ef1112a063dfc25203"}

[commit-bot: I haz the power, 2017-06-14 20:33:44]

Description was changed from

==========
Fix the crash that happens if the default wallpaper image decoding failed.

BUG=725667
==========

to

==========
Fix the crash that happens if the default wallpaper image decoding failed.

BUG=725667

Review-Url: https://codereview.chromium.org/2931063003
Cr-Commit-Position: refs/heads/master@{#479490}
Committed:
https://chromium.googlesource.com/chromium/src/+/26f7ab8456c7e21751bd55ef1112...
==========

[commit-bot: I haz the power, 2017-06-14 20:33:47]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/26f7ab8456c7e21751bd55ef1112...