Fix phishing attacks over Bluetooth due to unclear warning message

This CL add more prompts presented for users to avoid phishing attacks.

Screenshot:
https://screenshot.googleplex.com/p5PZbphN46ddPFV.png
https://screenshot.googleplex.com/6Q2wKfPbNQmTtx8.png
https://screenshot.googleplex.com/987VpYgNUZL2K4T.png
https://screenshot.googleplex.com/9eVg6SAGScVXU8U.png

Bug: 167403112
Test: manually test
Change-Id: Iadec059b662fd91754ad573bbe688702cdd3c9af