GC-related V8 APIs will change

[ma...@chromium.org]

Hi v8-users,

We're going to change a couple of garbage collection related V8 APIs.
We did these changes because we're also going to make Persistent
handles non-copyable in the near future. This is a step towards the
embedder not needing to copy Persistent handles around when giving V8
information it needs for doing the GC.

The new APIs will be present and the old ones deprecated in V8 version 3.18.

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Here's a summary of the changes:

Old: V8::AddObjectGroup

Replacement: Isolate::SetObjectGroupId, HeapProfiler::SetRetainedObjectInfo

With the old APIs, you'd tell V8 "these object belong to the same
group". With the new APIs, you just need to tell V8 the "color" of
each object, and V8 will take care of the grouping.

Old: V8::AddImplicitReferences

Replacement: Isolate::SetReference, Isolate::SetReferenceFromGroup

With the old APIs, you could only add references between objects. With
the new APIs, you can also add a reference from an object group.

The old APIs will be deprecated and then removed. The new APIs are
available in V8 bleeding edge.

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We don't expect any other embedder than Blink to use these APIs.
Please reply to this e-mail if you are aware of another embedder which
uses them, and especially if the changes will cause problems.

BR,
ma...@chromium.org