UserImageLoader: Remove DCHECK requiring success of ReadFileToString().

UserImageLoader: Remove DCHECK requiring success of ReadFileToString().

The case of a non-existing image file should be treated as an ordinary error case, just as a garbled JPEG image would be.

Update comment for UserImageLoader::Start() accordingly.

(The current behaviour breaks out/Debug/chrome (no parameters) compiled with chromeos=1.)

BUG=371295
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269903

[Thiemo Nagel, 2014-04-30 13:00:44]

Hi Bartosz,

I'm sending this to you because you contributed the line in question.  Could you
please take a look?

Thank you!
Thiemo

[bartfab (slow), 2014-05-05 10:10:10]

lgtm

[Thiemo Nagel, 2014-05-05 10:17:57]

Hi Pavel,

could you please be so kind to take a look at this small CL?

Thank you!
Thiemo

[Thiemo Nagel, 2014-05-12 10:00:01]

Hi Pavel,

may I ping you about this CL again?  It's just a small fix.

Best regards,
Thiemo

[dzhioev (left Google), 2014-05-12 13:10:27]

On 2014/05/12 10:00:01, Thiemo Nagel wrote:
> Hi Pavel,
> 
> may I ping you about this CL again?  It's just a small fix.
> 
> Best regards,
> Thiemo

Sorry, I was on vacation since April 29.

Do you know who was trying to load non-existing image file?

[Thiemo Nagel, 2014-05-12 13:56:56]

On 2014/05/12 13:10:27, dzhioev wrote:
> Sorry, I was on vacation since April 29.

No problem, it's not urgent.
 
> Do you know who was trying to load non-existing image file?

It seems that running "chrome" (without cmdline parameters) when compiled with
CHROMEOS=1 will try to access local config.  In my case, the UserImageLoader
tries to open the non-existing file
/usr/local/google/home/tnagel/.config/chromium/tnagel@google.com.jpg.

This is not my main point, though:  In real world scenarios, it can happen that
the profile image disappears (eg. due to filesystem corruption) and the
corresponding code path should handle that case gracefully.  In my opinion, it
is not correct to have a DCHECK() in a legitimate error path.

[dzhioev (left Google), 2014-05-12 15:46:49]

On 2014/05/12 13:56:56, Thiemo Nagel wrote:
> On 2014/05/12 13:10:27, dzhioev wrote:
> > Sorry, I was on vacation since April 29.
> 
> No problem, it's not urgent.
>  
> > Do you know who was trying to load non-existing image file?
> 
> It seems that running "chrome" (without cmdline parameters) when compiled with
> CHROMEOS=1 will try to access local config.  In my case, the UserImageLoader
> tries to open the non-existing file
> mailto:/usr/local/google/home/tnagel/.config/chromium/tnagel@google.com.jpg.
> 
> This is not my main point, though:  In real world scenarios, it can happen
that
> the profile image disappears (eg. due to filesystem corruption) and the
> corresponding code path should handle that case gracefully.  In my opinion, it
> is not correct to have a DCHECK() in a legitimate error path.

(It is a bad idea to run "chromeos=1" build without arguments. You should
provide
--user-data-dir=PATH and --login-profile=user (or --multi-profiles) at least.)

Please log error message containing file name if reading from file was failed.
LGTM after that.

[Thiemo Nagel, 2014-05-12 16:07:52]

> (It is a bad idea to run "chromeos=1" build without arguments. You should
> provide
> --user-data-dir=PATH and --login-profile=user (or --multi-profiles) at least.)

It's good to remember that.
 
> Please log error message containing file name if reading from file was failed.
> LGTM after that.

Done.  Thank you!

[Thiemo Nagel, 2014-05-12 16:07:56]

The CQ bit was checked by tnagel@chromium.org

[commit-bot: I haz the power, 2014-05-12 16:08:38]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tnagel@chromium.org/264483004/40001

[commit-bot: I haz the power, 2014-05-12 20:43:08]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  win_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_rel/buil...)

[commit-bot: I haz the power, 2014-05-12 23:07:02]

Change committed as 269903