Add the host attribute to the html5 ShadowRoot type.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67702766
ES6: Add support for spread expressions in the NewIRFactory, CodeGenerator, and AstValidator.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67712082
Updated code.google.com links to developer.chrome.com
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67713244
Move the languageIn/languageOut checking to Compiler, so that Es6ToEs3Converter only contains the actual transpilation logic.

This also checks for invalid language-in/language-out combinations: If the two languages don't match, the input language must be ES6 and the output must be ES3.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67716201
[NEW TYPE INFERENCE] Bugfixes for hasNonScalar and removeType.

- Handle enums in hasNonScalar.
- removeType should remove subtypes of its argument, eg, to handle cases like 'function' or 'object' in typeof.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67718116
Enable gatherExternsFromTypes by default.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67720142
Add support for class expressions and statics.

This is part of #419.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=67722810