Small cleanup in SearchBoxView::HandleKeyEvent

Moves key handling for the case SearchBoxSelection feature is disabled
to a separate method. This makes it easier to follow feature specific
parts of the logic (and make subsequent changes to the key handler
easier).

BUG=939106

Change-Id: I52ed5f2a1458d281f89249eff656f4404b0fb8b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1737807Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684386}

ash/app_list/views/search_box_view.h

@@ -152,6 +152,12 @@ class APP_LIST_EXPORT SearchBoxView : public search_box::SearchBoxViewBase,
   // Clear highlight range.
   void ResetHighlightRange();
 
+  // Key event handler used when SearchBoxSelection feature is disabled. This
+  // should be removed when the app_list_features::IsSearchBoxSelectionEnabled()
+  // flag is removed.
+  bool HandleKeyEventForDisabledSearchBoxSelection(
+      const ui::KeyEvent& key_event);
+
   // The range of highlighted text for autocomplete.
   gfx::Range highlight_range_;