src: fix path for Go modules mode compatibility

Switching to Go modules mode, which is the default dep
management mode in newer Go versions, requires that all
non standard-library import paths be prefixed with an URL.

This is due to the the fact that direct import paths are
now reserved strictly for the Go standard library pkgs
and all non-std pkgs are required to have an URL prefix.

Renaming the filesystem path itself (not just the import
directives) is required because we are still using GOPATH
mode fow now and will enable the transition gradually in
all CrOS projects.

BUG=b:187795288
TEST=Local builds; CQ.

Cq-Depend: chromium:3673616
Change-Id: I393a4cc3c7735b9fe9fd9f8fca4273e790619570
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/graphics/+/3673319
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Auto-Submit: Adrian Ratiu <adrian.ratiu@collabora.corp-partner.google.com>
Reviewed-by: Po-Hsien Wang <pwang@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
76 files changed