split view: Remove kSplitviewAnimationDurationMs

kSplitviewAnimationDurationMs is unused.

Test: manual
Change-Id: I3206f1a4cbb777ed4b30ca30d4d58acd47aa217f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1601422Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Avery Musbach <amusbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658777}

ash/wm/splitview/split_view_constants.h

@@ -35,8 +35,6 @@ constexpr SkColor kSplitviewLabelEnabledColor = SK_ColorWHITE;
 constexpr SkColor kSplitviewLabelBackgroundColor =
     SkColorSetA(SK_ColorBLACK, 0xDE);
 
-constexpr int kSplitviewAnimationDurationMs = 250;
-
 }  // namespace ash
 
 #endif  // ASH_WM_SPLITVIEW_SPLIT_VIEW_CONSTANTS_H_