app_list: Reset search result page opacity in ResetForShow

The search result page opacity might get set to a partially opaque
value during app list drag - this resets the opacity to 1.0 before
showing app list view again (in case the app list was dragged really
close to shelf before closing, in which case last opacity set on the
layer might have been small).
This should not affect initial search result page appearance (as
the page starts in invisible state).

BUG=1027805

Change-Id: I7a5fbd22647f976a22a39aa61a4f44ab03756215
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1936108Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720745}

ash/app_list/views/contents_view.cc

@@ -176,6 +176,9 @@ void ContentsView::ResetForShow() {
   // SetActiveState() since it checks the visibility of the pages.
   horizontal_page_container_->SetVisible(true);
   search_results_page_view_->SetVisible(false);
+  // SearchBoxView::UpdateOpacity() may change search result page opacity during
+  // drag - make sure that opacity value is reset to 1.0f.
+  search_results_page_view_->layer()->SetOpacity(1.0f);
   if (assistant_page_view_)
     assistant_page_view_->SetVisible(false);
   SetActiveState(ash::AppListState::kStateApps, /*animate=*/false);