Bug 865005 - Part 1: Refactor initialization and create loadStartupTab() for initial tab. r=mfinkle
Bug 865005 - Part 2: Use SessionRestoreException to avoid swallowing unrelated exceptions. r=mfinkle
Bug 865005 - Part 3: Move session restore code into restoreSessionTabs(). r=mfinkle
Bug 865005 - Part 4: Merge multiple session strings before restoring. r=mfinkle