[Blob] Better error reporting and histograms.

[Blob] Better error reporting and histograms.

The UMA for renderer crashes due to invalid blob messages
is rather high. I'm adding better error reporting to figure
out the issue.

BUG=602443
Committed: https://crrev.com/907439e58214fcdf4759296655ce650ad4f0eb86
Cr-Commit-Position: refs/heads/master@{#386754}

[dmurph, 2016-04-11 21:20:50]

Description was changed from

==========
[Blob] Better error reporting and histograms

BUG=602443
==========

to

==========
[Blob] Better error reporting and histograms.

The UMA for renderer crashes due to invalid blob messages
is rather high. I'm adding better error reporting to figure
out the issue.

BUG=602443
==========

[dmurph, 2016-04-11 21:22:27]

dmurph@chromium.org changed reviewers:
+ kinuko@chromium.org, mpearson@chromium.org

[dmurph, 2016-04-11 21:22:27]

Hi Mark & Kinuko!

I'm trying to add better error reporting so that I can figure out what's
happening with blobs.
Kinuko: Can you look at the content/* files?
Mark: I'm adding the bad message enum, but I'm also fixing a couple 'units' to
'enum' keywords. Is this change OK to do? I'm assuming it only changes the way
the data is interpreted, so it shouldn't mess anything up.


Thanks!
Daniel

[Mark P, 2016-04-11 21:32:39]

What you're doing with the enum is, metrics-wise, a bit of a mess.  You'll have
enum bucket 17 mean on thing in certain versions of Chrome and something else in
other versions.

The normal thing I'd suggest here is simply deprecate the old value 17 and add
two new values, 18 and 19.

However, this is still a mess because you're also trying to change a previous
emit of a bucket 17 to an emit of a bucket 17 (BDH_CONSTRUCTION_FAILED).

In complex cases like this the best practice is to rename the histogram, marking
the old name as obsolete, for a clean break between old semantics and new.

--mark

https://codereview.chromium.org/1875223002/diff/1/content/browser/bad_message.h
File content/browser/bad_message.h (right):

https://codereview.chromium.org/1875223002/diff/1/content/browser/bad_message...
content/browser/bad_message.h:141: BDH_INVALID_REFCOUNT_OPERATION = 117,
I assume this change is just for clarity, right?  It's not actually changing
when enum number 17 is emitted?

[Mark P, 2016-04-11 23:17:41]

histograms.xml lgtm / approval on condition that you get this merged with the
change that landed the BDH_ logging.  I don't wants metrics to change their
meeting between major Chrome milestones.

--mark

[kinuko, 2016-04-12 05:09:12]

lgtm if Mark is fine with the histogram change

[dmurph, 2016-04-12 17:40:12]

The CQ bit was checked by dmurph@chromium.org

[commit-bot: I haz the power, 2016-04-12 17:40:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1875223002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1875223002/1

[commit-bot: I haz the power, 2016-04-12 18:46:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-12 18:47:36]

Description was changed from

==========
[Blob] Better error reporting and histograms.

The UMA for renderer crashes due to invalid blob messages
is rather high. I'm adding better error reporting to figure
out the issue.

BUG=602443
==========

to

==========
[Blob] Better error reporting and histograms.

The UMA for renderer crashes due to invalid blob messages
is rather high. I'm adding better error reporting to figure
out the issue.

BUG=602443

Committed: https://crrev.com/907439e58214fcdf4759296655ce650ad4f0eb86
Cr-Commit-Position: refs/heads/master@{#386754}
==========

[commit-bot: I haz the power, 2016-04-12 18:47:37]

Patchset 1 (id:??) landed as
https://crrev.com/907439e58214fcdf4759296655ce650ad4f0eb86
Cr-Commit-Position: refs/heads/master@{#386754}