Allow generated externs to use '?'.

R=nicksantos
DELTA=219 (112 added, 49 deleted, 58 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=6144


git-svn-id: http://closure-compiler.googlecode.com/svn/trunk@2468 b0f006be-c8cd-11de-a2e8-8d36a3108c74

Small update to chrome extensions extern
Contributed by amattie
Fixes issue 876
https://code.google.com/p/closure-compiler/issues/detail?id=876
try #2
Makes all the parameters of chrome.windows.* optional.
Updates some testing code.

R=ewa,kashida
DELTA=51 (13 added, 12 deleted, 26 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=6145


git-svn-id: http://closure-compiler.googlecode.com/svn/trunk@2469 b0f006be-c8cd-11de-a2e8-8d36a3108c74