DevTools: [MediaQueryInspector] Compute media query length on backend

DevTools: [MediaQueryInspector] Compute media query length on backend

This patch pulls computed media query lengths values from backend.
Note: it is ok to create multiple MediaValuesDynamic objects because
they don't have any internal state and serve as a helper wrappers.

BUG=382996
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176445

[lushnikov, 2014-06-18 12:53:23]

ptal

[pfeldman, 2014-06-18 14:38:16]

lgtm

[lushnikov, 2014-06-18 14:42:11]

The CQ bit was checked by lushnikov@chromium.org

[commit-bot: I haz the power, 2014-06-18 14:42:54]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/lushnikov@chromium.org/339553004/1

[commit-bot: I haz the power, 2014-06-18 16:48:49]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-06-18 16:48:50]

Try jobs failed on following builders:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)

[lushnikov, 2014-06-18 18:29:46]

The CQ bit was checked by lushnikov@chromium.org

[commit-bot: I haz the power, 2014-06-18 18:30:54]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/lushnikov@chromium.org/339553004/1

[commit-bot: I haz the power, 2014-06-18 19:36:47]

Change committed as 176445