Update externs for jasmine.js.

Fixes issue 994.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=46644098
Further improve performance of MinimizeConditions.

Keep track of which trees are changed/unchanged when building the
minimized condition trees, and use this information instead of
calling the expensive Node.isEquivalentTo() method to determine
if there are changes to the AST.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=46692215