Disable eager tracing for NGPhysicalFragment.

By default Oilpan has a limit on stackFrameDepth while tracing
HeapVector. Wrap NGPhysicalFragment into TraceEagerlyTrait class to fix that.

BUG=635619

Review-Url: https://codereview.chromium.org/2372573006
Cr-Commit-Position: refs/heads/master@{#421263}
1 file changed