Encrypted Media: Add UMA for system code.

Encrypted Media: Add UMA for system code.

Choose to put the UMA reporting code in content_decryptor_delegate.cc because:
- It's hard to do UMA in CdmAdapter due to pp::UMAPrivate limitations.
- I want to report system code for OnPromiseRejected() and OnSessionError() in
  one file. So I can't do it in CdmPromise.

BUG=412987
TEST=Tested by hacking Chromium to provide a wrong license. Then check about://histograms and I see the histogram generated.

Committed: https://crrev.com/f1914fab8e95ac880b28dd521299f5fc3f72704d
Cr-Commit-Position: refs/heads/master@{#294478}

[xhwang, 2014-09-10 21:14:06]

xhwang@chromium.org changed reviewers:
+ ddorwin@chromium.org

[xhwang, 2014-09-10 21:14:17]

PTAL

[ddorwin, 2014-09-10 21:24:34]

The code looks fine, but I'm not sure we can include media/crypto/ files here.
It's really unfortunate that we would need to have such code in a pepper/
directory. How bad would it be to have this in CdmPromise and where keyerrors
are reported?

https://codereview.chromium.org/561643002/diff/1/content/renderer/pepper/cont...
File content/renderer/pepper/content_decryptor_delegate.cc (right):

https://codereview.chromium.org/561643002/diff/1/content/renderer/pepper/cont...
content/renderer/pepper/content_decryptor_delegate.cc:12: #include
"content/renderer/media/crypto/key_systems.h"
Is this allowed? crypto/ is not in src/content/renderer/pepper/DEPS.

https://codereview.chromium.org/561643002/diff/1/tools/metrics/histograms/his...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/561643002/diff/1/tools/metrics/histograms/his...
tools/metrics/histograms/histograms.xml:11257: +<histogram
name="Media.EME.ClearKey.SystemCode" units="system code">
This will never occur because of where the code is.

[xhwang, 2014-09-10 22:08:55]

comments addressed

[xhwang, 2014-09-10 22:09:34]

PTAL again.

https://codereview.chromium.org/561643002/diff/1/content/renderer/pepper/cont...
File content/renderer/pepper/content_decryptor_delegate.cc (right):

https://codereview.chromium.org/561643002/diff/1/content/renderer/pepper/cont...
content/renderer/pepper/content_decryptor_delegate.cc:12: #include
"content/renderer/media/crypto/key_systems.h"
On 2014/09/10 21:24:34, ddorwin wrote:
> Is this allowed? crypto/ is not in src/content/renderer/pepper/DEPS.

It seems this IS allowed.

https://codereview.chromium.org/561643002/diff/1/tools/metrics/histograms/his...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/561643002/diff/1/tools/metrics/histograms/his...
tools/metrics/histograms/histograms.xml:11257: +<histogram
name="Media.EME.ClearKey.SystemCode" units="system code">
On 2014/09/10 21:24:34, ddorwin wrote:
> This will never occur because of where the code is.

Removed.

[ddorwin, 2014-09-10 22:27:27]

lgtm

[xhwang, 2014-09-10 23:43:17]

xhwang@chromium.org changed reviewers:
+ dmichael@chromium.org, isherman@chromium.org

[xhwang, 2014-09-10 23:43:18]

dmichael: Please OWNERS review
content/renderer/pepper/content_decryptor_delegate.cc.

isherman: Please OWNERS review  tools/metrics/histograms/histograms.xml

[Ilya Sherman, 2014-09-11 05:15:29]

LGTM % a suggestion:

https://codereview.chromium.org/561643002/diff/20001/tools/metrics/histograms...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/561643002/diff/20001/tools/metrics/histograms...
tools/metrics/histograms/histograms.xml:11308: +<histogram
name="Media.EME.Unknown.SystemCode" units="system code">
For these histograms, it would be more useful to associate an enum that
translates system codes into something that humans might understand, rather than
just stating that these are system codes and requiring users to go digging for
the mapping.

[dmichael (off chromium), 2014-09-11 19:14:14]

OWNERS lgtm, but +1 to Ilya's suggestion.

[xhwang, 2014-09-11 20:04:42]

The CQ bit was checked by xhwang@chromium.org

[commit-bot: I haz the power, 2014-09-11 20:07:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/561643002/20001

[commit-bot: I haz the power, 2014-09-11 22:22:38]

Committed patchset #2 (id:20001) as 985c0d6f37c121d894ff5cf45b38b45684018d94

[commit-bot: I haz the power, 2014-09-11 22:31:08]

Patchset 2 (id:??) landed as
https://crrev.com/f1914fab8e95ac880b28dd521299f5fc3f72704d
Cr-Commit-Position: refs/heads/master@{#294478}