Added StereoPannerNode to the Web Audio externs.

This interface is already available in Canary.

http://webaudio.github.io/web-audio-api/#the-stereopannernode-interface
Merge pull request #725 from creative-monkey/patch-1

Added StereoPannerNode to the Web Audio externs.
Mark the conformance configs command line option as hidden so it doesn't show in the sample usage shown on flag errors.
Merge pull request #728 from ChadKillingsworth/hide-extra-option

Mark the conformance configs command line option as hidden
Update ALL_NATIVE_EXTERN_TYPES code to keep it in sync with externs
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=80845803
[NEW TYPE INFERENCE] Support general constructors with @return
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=80850963
Allow unknown "this" values to be checked using assert methods.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=80867015
Remove Module from FunctionInformationMap. This is duplicated from other compiler outputs.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=80871576
Externs for Maps API v3.19.1.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=81038649
Add angular.$routeProvider.Params.controllerAs
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=81082050
Add back some unused code
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=81194354
Add angular.NgModelController.prototype.$asyncValidators
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=81205387