API DebugToolbar's debugLog format cleanup

When using debug toolbar, make the result cleaner and more readable:

XML: <debugLog><msg>…</msg><msg>…</msg></debugLog>
JSON: "debugLog": ["…","…"]

Instead of current:
XML: <debugLog><msg xml:space="preserve">…</msg>...
JSON: "debugLog": [{"*": "…"}, {"*": "…"}]

Change-Id: Ieb9d3ab23d7654f5eaf3b79b3b69f4aab99d4680
Merge "API DebugToolbar's debugLog format cleanup"