Add DragEvent to the HTML5 externs.

As best I can tell, this was introduced as part of HTML5.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65019521
Don't crash on typical jsdoc method declarations.

This quick fix skips type checking on these cases, which
we will clearly need to come back to.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65023390
[NEW TYPE INFERENCE] Fixing ported tests.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65026070
Remove jslayoutjs annotation.  It is no longer needed for jslayout_js
edit/refresh support.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65058001
Remove some unused code
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=65064847