git isn’t installed on your system. The reason you got the error message is because certain build requirements aren’t automatically installed for you and you need to do it manually.
(although I confess being a bit confused because I was pretty sure git was a default manjaro package.)
Which is most unfortunate of you. There should be no problem for you to get it. But like others said, you seem to be lacking very basic information to become an AUR user. And this will only ruin your system.
If you don’t mind that, then go ahead and install git, then try Chrome again.
If you do not wan to risk your system at this point, it is perhaps best if you use another distro where Chrome is a part of the repositories, or if you want to stick to Arch-based distros, switch to Antergos which I believe has Chrome as an option in its installer.