BlinkGCPlugin: Fix base class trace call detection in traceImpl().

BlinkGCPlugin: Fix base class trace call detection in traceImpl().

Existing code has assumed a trace function call delegating to a base class has
the same name as the name of the function where the trace call is written (e.g.
Base::trace(visitor) in Derived::trace(), and Base::traceAfterDispatch(visitor)
in Derived::traceAfterDispatch()).

After the introduction of traceImpl(), however, this is no longer true. This
patch fixes this issue.

BUG=none
R=kouhei@chromium.org
CC=zerny@chromium.org, oilpan-reviews@chromium.org

Committed: https://crrev.com/d8c277946ff3cb54a256a77c38d60373f14dee29
Cr-Commit-Position: refs/heads/master@{#317026}

[kouhei (in TOK), 2015-02-19 10:59:47]

The CQ bit was checked by kouhei@chromium.org

[kouhei (in TOK), 2015-02-19 10:59:48]

lgtm

[commit-bot: I haz the power, 2015-02-19 11:00:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/935253002/1

[commit-bot: I haz the power, 2015-02-19 11:03:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-19 11:04:28]

Patchset 1 (id:??) landed as
https://crrev.com/d8c277946ff3cb54a256a77c38d60373f14dee29
Cr-Commit-Position: refs/heads/master@{#317026}