RegExpCompileEvent acquieres mutex from Log class during MessageBuilder creation. LogRegExpSource, called from RegExpCompileEvent creates another MessageBuilder object which also acquires the same mutex. This mutex is not recursive, so during second acquirement, assertion fail is happening. Solution: LogRegExpSource should use the same MessageBuilder object as RegExpCompileEvent.

Review URL: https://codereview.chromium.org/1207433002

Cr-Commit-Position: refs/heads/master@{#29347}