[iOS] Tune updated new tab animation

A small tweak to the spring damping ratio for the new tab animation, which ensures that the spring effect doesn't show a black hairline on an iPhone X.

Bug: 851872
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I1b6769f9d4b124e332efddf2f9602b4665d7aca8
Reviewed-on: https://chromium-review.googlesource.com/1146640
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#577156}(cherry picked from commit 946179d)
Reviewed-on: https://chromium-review.googlesource.com/1149800
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/branch-heads/3497@{#65}
Cr-Branched-From: 271eaf5-refs/heads/master@{#576753}

ios/chrome/browser/ui/tabs/foreground_tab_animation_view.mm

@@ -12,7 +12,7 @@
 
 namespace {
 const NSTimeInterval kAnimationDuration = 0.75;
-const CGFloat kTabMotionDamping = 0.7;
+const CGFloat kTabMotionDamping = 0.75;
 const CGFloat kTabFadeInRelativeDuration = 0.4;
 const CGFloat kBackgroundFadeRelativeDuration = 0.33;
 const CGFloat kCornerRoundingRelativeDuration = 0.33;