BlinkGCPlugin: Fix detection of trace dispatching after inlined tracing.

BlinkGCPlugin: Fix detection of trace dispatching after inlined tracing.

This patch actually fixes three different issues, as I could not separate the
updated tests in a meaningful way.

1. CheckDispatchVisitor needs to look for UnresolvedMemberExpr*, since inlined
tracing introduces unresolved member references.

This visitor looks at every function call within a trace dispatching method,
and returns whether there is a call delegating to the class in question. We
need to take care of UnresolvedMemberExpr* cases in addition to MemberExpr*.

2. RecordInfo::DetermineTracingMethods() should return traceImpl() instead of
trace() as trace_dispatch_method_.

The plugin inspects the definition of trace_dispatch_method_ in order to detect
missing or inappropriate delegation to subclasses. Therefore, the method should
be something that has actual delegation calls in its body (i.e. traceImpl())
instead of a trampoline stub (i.e. trace()).

3. A silly typo in Config::GetTraceMethodType(). Really silly. Not sure why
I did this way.

This patch comes with updated tests for traceAfterDispatchImpl(). Now the tests
are more closer to real cases, using traceImpl to implement trace dispatching.

BUG=462511
R=kouhei@chromium.org
CC=zerny@chromium.org, oilpan-reviews@chromium.org

Committed: https://crrev.com/8747aee1f18410d8eaf0e2d98724c8e24477bdc2
Cr-Commit-Position: refs/heads/master@{#318673}

[Yuta Kitamura, 2015-03-02 09:15:43]

Note: this is the last change needed to fix all known
inlined-trace-related issues.

[kouhei (in TOK), 2015-03-02 09:26:05]

lgtm. Thanks a lot!

[kouhei (in TOK), 2015-03-02 09:26:19]

The CQ bit was checked by kouhei@chromium.org

[commit-bot: I haz the power, 2015-03-02 09:26:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/968143002/1

[commit-bot: I haz the power, 2015-03-02 09:59:24]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-02 10:00:15]

Patchset 1 (id:??) landed as
https://crrev.com/8747aee1f18410d8eaf0e2d98724c8e24477bdc2
Cr-Commit-Position: refs/heads/master@{#318673}