Disable kExperimentalFlingAnimation for lacros-Chrome.

Lacros-Chrome and ChromeOS-Chrome use different animation curves
for fling scroll.
To make them consistent, this disables ExperimentalFlingAnimation
flag for Lacros-Chrome as ChromeOS-Chrome doesn't enable it.

Bug: 1129263
Change-Id: Ibe4c80f08f077a951e529f3a670f7db914dc1394
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2439816Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813033}

ui/base/ui_base_features.cc

@@ -100,7 +100,8 @@ const base::Feature kCompositorThreadedScrollbarScrolling = {
 // native apps on Windows.
 const base::Feature kExperimentalFlingAnimation {
   "ExperimentalFlingAnimation",
-#if defined(OS_WIN) || (defined(OS_LINUX) && !defined(OS_CHROMEOS))
+#if defined(OS_WIN) || \
+    (defined(OS_LINUX) && !defined(OS_CHROMEOS) && !BUILDFLAG(IS_LACROS))
       base::FEATURE_ENABLED_BY_DEFAULT
 #else
       base::FEATURE_DISABLED_BY_DEFAULT