Fix search box's overlap with suggestion chip

Changes:
Update the y positions of child views to target state upon animation
start to avoid stale positions.

Bug: 901168
Change-Id: I605d20302a7512b82ffe5cf445e7166f64da3280
Reviewed-on: https://chromium-review.googlesource.com/c/1315810
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605053}

ash/app_list/presenter/app_list_presenter_impl.cc

@@ -243,6 +243,9 @@ void AppListPresenterImpl::UpdateYPositionAndOpacityForHomeLauncher(
   }
   layer->SetOpacity(opacity);
   layer->SetTransform(translation);
+
+  // Update child views' y positions to target state to avoid stale positions.
+  view_->app_list_main_view()->contents_view()->UpdateYPositionAndOpacity();
 }
 
 void AppListPresenterImpl::ScheduleOverviewModeAnimation(bool start,

ash/app_list/views/app_list_view.cc

@@ -1260,9 +1260,9 @@ void AppListView::StartAnimationForState(AppListViewState target_state) {
   layer->SetTransform(gfx::Transform());
 
   // In transition animation, layout is only performed after it is complete,
-  // which makes the child views jump. So layout in advance here to avoid that.
-  GetAppsContainerView()->InvalidateLayout();
-  Layout();
+  // which makes the child views jump. So update y positions in advance here to
+  // avoid that.
+  app_list_main_view_->contents_view()->UpdateYPositionAndOpacity();
 }
 
 void AppListView::StartCloseAnimation(base::TimeDelta animation_duration) {

ash/app_list/views/apps_grid_view.cc

@@ -1945,9 +1945,11 @@ void AppsGridView::UpdateOpacity() {
   // changes from 0.f to 1.0f.
   const float peeking_to_fullscreen_height =
       app_list_view->GetFullscreenStateHeight() - peeking_height;
-  DCHECK_GT(peeking_to_fullscreen_height, 0);
   const float drag_amount = current_height - peeking_height;
-  fraction = std::max(drag_amount / peeking_to_fullscreen_height, 0.f);
+  fraction = std::max(peeking_to_fullscreen_height > 0
+                          ? drag_amount / peeking_to_fullscreen_height
+                          : 1.0f,
+                      0.f);
   opacity = std::min(std::max((fraction + kAllAppsIndicatorOpacityEndFraction -
                                kAllAppsIndicatorOpacityStartFraction - 1.0f) /
                                   (kAllAppsIndicatorOpacityEndFraction -