Oilpan: move WorkerInspectorController's frontend channel to the heap.

Move along this WorkerInspectorController-owned object to the heap also,
allowing it to keep a traced reference to its worker global scope.

R=haraken
BUG=553613

Review URL: https://codereview.chromium.org/1449963002

Cr-Commit-Position: refs/heads/master@{#360052}
2 files changed