Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/Source/bindings/IDLExtendedAttributes.md

 # Blink IDL Extended Attributes
 
 [TOC]
 
 ## Introduction
 
 The main interest in extended attributes are their _semantics_: Blink implements many more extended attributes than the Web IDL standard, to specify various behavior.
 
 The authoritative list of allowed extended attributes and values is [bindings/IDLExtendedAttributes.txt](https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/bindings/IDLExtendedAttributes.txt). This is complete but not necessarily precise (there may be unused extended attributes or values), since validation is run on build, but coverage isn't checked.
 
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 Usage: `[DeprecateAs]` can be specified on methods, attributes, and constants.
 
 ```webidl
     [DeprecateAs=DeprecatedPrefixedAttribute] attribute Node prefixedAttribute;
     [DeprecateAs=DeprecatedPrefixedMethod] Node prefixedGetInterestingNode();
     [DeprecateAs=DeprecatedPrefixedConstant] const short DEPRECATED_PREFIXED_CONSTANT = 1;
 ```
 
 The deprecation message show on the console can be specified via the [UseCounter::deprecationMessage](https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/core/frame/UseCounter.cpp&q=UseCounter::deprecationMessage&l=615) method.
 
-### [GarbageCollected] _(i)_
-
-Summary: The `[GarbageCollected]` attribute signals that the object is kept on the Oilpan heap and handled by its garbage collector.
-
-Usage: `[GarbageCollected]` can be specified on interfaces, and is inherited:
-
-```webidl
-[
-    GarbageCollected,
-] interface BatteryManager { ... };
-```
-
-In order to generate correct binding layer code for an interface, `[GarbageCollected]` must be supplied if the object is an Oilpan-based object.
-
-
 ### [Iterable] _(i)_
 
 Summary: Installs a @@iterator method.
 
 *** note
 In most cases, interfaces should use the standard `iterator<valuetype>`, `iterator<keytype,valuetype>`, `setlike<type>`, or `maplike<keytype, valuetype>` IDL declarations instead. `[Iterable]` should only be necessary for the implementation of iterators themselves.
 ***
 
 When the attribute is set on an interface, the code generator installs iterator C++ method into [Symbol.iterator] slot.
 
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 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
 
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 ***