CSP 1.1: Introduce the 'child-src' directive.

CSP 1.1: Introduce the 'child-src' directive.

The 'child-src' directive deprecates 'frame-src', and will take over governance
of nested and auxiliary browsing contexts, as well as Workers. This patch 
introduces the new directive, and sets things up such that frame checks properly
hit first 'frame-src', then 'child-src', then 'default-src' (if the CSP flag is set).

Future patches will address Workers, `window.open`, and etc.

BUG=336788
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165762

[Mike West, 2014-01-23 09:36:06]

Hey Jochen, Adam,

Mind taking a look at this CL?

-mike

[abarth-chromium, 2014-01-23 20:53:05]

lgtm

[commit-bot: I haz the power, 2014-01-24 15:51:13]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mkwst@chromium.org/131103010/100001

[commit-bot: I haz the power, 2014-01-24 18:00:57]

Change committed as 165762