Slight reduction in string copying for WebRTC stats.

Slight reduction in string copying for WebRTC stats.
* Only call ToString() for types that require conversion to string. If the value is already of type string, we can just use that value.

* For chrome://webrtc-internals, we can now pass the correct type in most cases (not in64), in the dictionary passed to the web page.  This also lowers the overhead of the PeerConnectionTracker when no page requires this data.  (I think we can still do better there though).

BUG=webrtc:2822
Committed: https://crrev.com/a5c0d763fd248d5ec8a8e5b837282bccfadd303a
Cr-Commit-Position: refs/heads/master@{#320772}

[tommi (sloooow) - chröme, 2015-03-13 19:12:53]

tommi@chromium.org changed reviewers:
+ perkj@chromium.org

[perkj_chrome, 2015-03-16 10:36:39]

lgtm

https://codereview.chromium.org/1009543003/diff/1/content/renderer/media/peer...
File content/renderer/media/peer_connection_tracker.cc (right):

https://codereview.chromium.org/1009543003/diff/1/content/renderer/media/peer...
content/renderer/media/peer_connection_tracker.cc:238: case
StatsReport::Value::kInt64:  // int64 isn't supported, so use string.
todo:tommi fix int64 support?

[tommi (sloooow) - chröme, 2015-03-16 18:07:41]

https://codereview.chromium.org/1009543003/diff/1/content/renderer/media/peer...
File content/renderer/media/peer_connection_tracker.cc (right):

https://codereview.chromium.org/1009543003/diff/1/content/renderer/media/peer...
content/renderer/media/peer_connection_tracker.cc:238: case
StatsReport::Value::kInt64:  // int64 isn't supported, so use string.
On 2015/03/16 10:36:39, perkj wrote:
> todo:tommi fix int64 support?

It's not supported by base::ListValue and apparently it would be a spec
violation if it did:
https://code.google.com/p/chromium/codesearch#chromium/src/base/values.h&l=12

[tommi (sloooow) - chröme, 2015-03-16 18:07:47]

The CQ bit was checked by tommi@chromium.org

[commit-bot: I haz the power, 2015-03-16 18:08:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1009543003/1

[commit-bot: I haz the power, 2015-03-16 19:21:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-16 19:21:57]

Patchset 1 (id:??) landed as
https://crrev.com/a5c0d763fd248d5ec8a8e5b837282bccfadd303a
Cr-Commit-Position: refs/heads/master@{#320772}