Bug 1753565 - Disable prefers-reduced-motion for tests. r=botond

Disable the prefers-reduced-motion preference for mochitests and
web-platform-tests.

Depends on D172446

Differential Revision: https://phabricator.services.mozilla.com/D174956

UltraBlame original commit: 6fb66b5e615328ae3841197e49d8e8f4b33c65f5

Author: marco-c

testing/profiles/mochitest/user.js

@@ -149,3 +149,30 @@ unsuppress_with_no_background
 true
 )
 ;
+/
+/
+Disable
+prefers
+-
+reduced
+-
+motion
+to
+ensure
+that
+smooth
+scrolls
+can
+be
+tested
+.
+user_pref
+(
+"
+general
+.
+smoothScroll
+"
+true
+)
+;

testing/profiles/web-platform/user.js

@@ -1063,3 +1063,30 @@ enabled
 0
 )
 ;
+/
+/
+Disable
+prefers
+-
+reduced
+-
+motion
+to
+ensure
+that
+smooth
+scrolls
+can
+be
+tested
+.
+user_pref
+(
+"
+general
+.
+smoothScroll
+"
+true
+)
+;