Reland of name AppRTCDemo on Android and iOS to AppRTCMobile (patchset #1 id:1 of https://codereview.webrtc.org/2358133003/ )

Reason for revert:
Internal project is updated.

Original issue's description:
> Revert of Rename AppRTCDemo on Android and iOS to AppRTCMobile (patchset #2 id:20001 of https://codereview.webrtc.org/2343403002/ )
>
> Reason for revert:
> Breaks internal project.
>
> Original issue's description:
> > Rename AppRTCDemo on Android and iOS to AppRTCMobile
> >
> > The purpose is to make it clearer it is a mobile application.
> >
> > BUG=webrtc:6359
> > NOPRESUBMIT=true
> >
> > Committed: https://crrev.com/d3af58bdab5b25acd62cd816363becc7003d3e5a
> > Cr-Commit-Position: refs/heads/master@{#14356}
>
> TBR=sakal@webrtc.org,kthelgason@webrtc.org,tommi@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:6359
>
> Committed: https://crrev.com/87ef6f750126f9f17f4714d696a8e77a2dd0a3f1
> Cr-Commit-Position: refs/heads/master@{#14358}

TBR=sakal@webrtc.org,kthelgason@webrtc.org,tommi@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:6359

Review URL: https://codereview.webrtc.org/2373443005 .

Cr-Original-Commit-Position: refs/heads/master@{#14391}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c1815cf084249976b93df39ece0d6616c252cd77
87 files changed