Blink GC plugin: improve handling of type dependent bases.

Blink GC plugin: improve handling of type dependent bases.

When exhaustively traversing the set of base classes for a class C,
the RecordInfo::IsGCDerived() method relied on the clang traversal method
used to support name lookups for a class. It will step over and ignore
any derived classes with dependent types as these are not to be considered
for that purpose.

In order to identify GC derived base classes for a definition like

 template<typename T>
 class A : public GarbageCollected<A> {
 public:
   // ..other needed stuff..
   class Local : public GarbageCollected<Local> { ... };
 };

and its nested class Local, traverse the base classes and if any
of them has a dependent type, resolve its dependent template and
use its class name when determining if it is a "GC derived" class.

For the above class, Local gets a dependent type when it is lifted
out of the class template by the AST visitor -- its type depending
on T.

R=
BUG=444740
Committed: https://crrev.com/a3d83dbb235465f5a8f2fe70a9f60b68fe5e055b
Cr-Commit-Position: refs/heads/master@{#309696}

[sof, 2014-12-28 22:57:27]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2014-12-28 22:57:27]

Please take a look.

Might be able to generalize slightly the treatment of dependently typed bases,
but this addresses all such classes in Blink atm.

[haraken, 2014-12-29 02:33:30]

LGTM

[haraken, 2014-12-29 02:33:34]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2014-12-29 02:34:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/827693004/1

[commit-bot: I haz the power, 2014-12-29 03:16:01]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-29 03:16:50]

Patchset 1 (id:??) landed as
https://crrev.com/a3d83dbb235465f5a8f2fe70a9f60b68fe5e055b
Cr-Commit-Position: refs/heads/master@{#309696}