applist-focus: Hitting Enter should activate the search box

Changes:
Hitting Enter when search box is not active and search box is focused
activates the search box.

BUG=780339
TEST=AppListViewFocusTest.HittingEnterWhenFocusOnSearchBox

Change-Id: I16d3b32d0d163badc11fc921926b2b174480c11e
Reviewed-on: https://chromium-review.googlesource.com/748164Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513189}

ui/app_list/views/app_list_view_unittest.cc

@@ -887,11 +887,18 @@ TEST_F(AppListViewFocusTest, FirstResultSelectedAfterSearchResultsUpdated) {
             contents_view()->search_results_page_view()->first_result_view());
 }
 
-// Tests that hitting Enter key when focus is on search box opens the first
-// result when it exists.
+// Tests hitting Enter key when focus is on search box.
+// There are two behaviors:
+// 1. Activate the search box when it is inactive.
+// 2. Open the first result when query exists.
 TEST_F(AppListViewFocusTest, HittingEnterWhenFocusOnSearchBox) {
   Show();
 
+  // Initially the search box is inactive, hitting Enter to activate it.
+  EXPECT_FALSE(search_box_view()->is_search_box_active());
+  SimulateKeyPress(ui::VKEY_RETURN, false);
+  EXPECT_TRUE(search_box_view()->is_search_box_active());
+
   // Type something in search box to transition to HALF state and populate
   // fake list results. Then hit Enter key.
   search_box_view()->search_box()->InsertText(base::UTF8ToUTF16("test"));

ui/app_list/views/search_box_view.cc

@@ -862,8 +862,8 @@ bool SearchBoxView::HandleKeyEvent(views::Textfield* sender,
                                    const ui::KeyEvent& key_event) {
   if (is_app_list_focus_enabled_) {
     if (key_event.type() == ui::ET_KEY_PRESSED &&
-        key_event.key_code() == ui::VKEY_RETURN &&
-        !IsSearchBoxTrimmedQueryEmpty()) {
+        key_event.key_code() == ui::VKEY_RETURN) {
+      if (!IsSearchBoxTrimmedQueryEmpty()) {
         // Hitting Enter when focus is on search box opens the first result.
         ui::KeyEvent event(key_event);
         views::View* first_result_view =
@@ -872,11 +872,18 @@ bool SearchBoxView::HandleKeyEvent(views::Textfield* sender,
                 ->first_result_view();
         if (first_result_view)
           first_result_view->OnKeyEvent(&event);
+        return true;
+      }
+
+      if (!is_search_box_active()) {
+        SetSearchBoxActive(true);
+        return true;
+      }
     }
-    // TODO(weidongg/766807) Remove this function when the flag is enabled by
-    // default.
     return false;
   }
+  // TODO(weidongg/766807) Remove everything below when the flag is enabled by
+  // default.
   if (key_event.type() == ui::ET_KEY_PRESSED) {
     if (key_event.key_code() == ui::VKEY_TAB &&
         focused_view_ != FOCUS_CONTENTS_VIEW &&