Add histograms about hub and spoke navigation usage

This CL adds logging for the following UMA histogram:
1. Tabs.Tasks.HubAndSpokeNavigationUsage.FromDefaultSearchEngine
2. Tabs.Tasks.HubAndSpokeNavigationUsage.FromFormSubmit
3. Tabs.Tasks.HubAndSpokeNavigationUsage.FromOthers

Bug: 856253
Change-Id: I2a83b0e4840c2435802815b3718a65155451d7a6
Reviewed-by: Ted Choc <>
Reviewed-by: Scott Violet <>
Reviewed-by: Wei-Yin Chen (陳威尹) <>
Reviewed-by: Yusuf Ozuysal <>
Reviewed-by: Ilya Sherman <>
Commit-Queue: Mei Liang <>
Cr-Commit-Position: refs/heads/master@{#576603}
8 files changed