ContentsView pagination model honours kPageTransitionDurationInMs.

This slows top-level app list page transitions from 120ms to 180ms.

BUG=406222

Review URL: https://codereview.chromium.org/559853003

Cr-Commit-Position: refs/heads/master@{#294126}

ui/app_list/views/contents_view.cc

@@ -32,6 +32,8 @@ ContentsView::ContentsView(AppListMainView* app_list_main_view)
       contents_switcher_view_(NULL),
       view_model_(new views::ViewModel),
       page_before_search_(0) {
+  pagination_model_.SetTransitionDurations(kPageTransitionDurationInMs,
+                                           kOverscrollPageTransitionDurationMs);
   pagination_model_.AddObserver(this);
 }