[Telemetry]: Move assert on page measurement results name into Value object.

[Telemetry]: Move assert on page measurement results name into Value object.

The use of a '.' in a trace name only breaks the telemetry value result if it
occurs in a value which does not have a trace_name.  This CL moves the assert
into the Value object so that the assert doesn't fire in other situations
(such as the media.tough_media_cases benchmark), where the use of the '.' is
actually ok.

BUG=332041, 329845
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243441

[rmcilroy, 2014-01-07 14:11:59]

Turns out the previous CL broke media.tough_media_case.  This fixes it, without
having to change the trace_names for media.tough_media_case.

[tonyg, 2014-01-07 17:00:48]

lgtm

[commit-bot: I haz the power, 2014-01-07 17:18:10]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rmcilroy@chromium.org/126013002/1

[commit-bot: I haz the power, 2014-01-07 17:38:21]

Retried try job too often on mac_rel for step(s) base_unittests, browser_tests,
interactive_ui_tests, net_unittests, unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...

[commit-bot: I haz the power, 2014-01-07 17:40:19]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rmcilroy@chromium.org/126013002/1

[commit-bot: I haz the power, 2014-01-07 22:35:19]

Retried try job too often on win_rel for step(s) nacl_integration
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2014-01-07 23:10:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rmcilroy@chromium.org/126013002/1

[commit-bot: I haz the power, 2014-01-08 00:10:55]

Change committed as 243441