Add extern for iframe srcdoc attribute.

This change is unlikely to break existing projects. The attribute is not widely used in google3:
https://cs.corp.google.com/#search/&q=usage:%22.srcdoc%20%22%20lang:js&type=cs
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=75670198
Add JQLite.css({...}) syntax to Angular externs files
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=75698856