App List: Refactor ContentsSwitcherView so it doesn't hard-code pages.

ui/app_list/views/contents_switcher_view.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/app_list/views/contents_switcher_view.h"
 
-#include "grit/ui_resources.h"
 #include "ui/app_list/app_list_constants.h"
 #include "ui/app_list/views/contents_view.h"
-#include "ui/base/resource/resource_bundle.h"
 #include "ui/views/controls/button/custom_button.h"
 #include "ui/views/controls/button/image_button.h"
 #include "ui/views/layout/box_layout.h"
 
 namespace app_list {
 
 namespace {
 
 const int kPreferredHeight = 32;
 const int kButtonSpacing = 4;
 
 }  // namespace
 
 ContentsSwitcherView::ContentsSwitcherView(ContentsView* contents_view)
     : contents_view_(contents_view), buttons_(new views::View) {
   AddChildView(buttons_);
 
   buttons_->SetLayoutManager(new views::BoxLayout(
       views::BoxLayout::kHorizontal, 0, 0, kButtonSpacing));
-  // TODO(mgiuca): Dynamically generate these buttons from the subviews of
-  // |contents_view|.
-  AddSwitcherButton(
-      IDR_APP_LIST_SEARCH_ICON,
-      contents_view->GetPageIndexForNamedPage(ContentsView::NAMED_PAGE_START));
-  AddSwitcherButton(
-      IDR_APP_LIST_APPS_ICON,
-      contents_view->GetPageIndexForNamedPage(ContentsView::NAMED_PAGE_APPS));
 }
 
 ContentsSwitcherView::~ContentsSwitcherView() {}
 
 void ContentsSwitcherView::AddSwitcherButton(int resource_id, int page_index) {
   views::ImageButton* button = new views::ImageButton(this);
-  button->SetImage(
-      views::CustomButton::STATE_NORMAL,
-      ui::ResourceBundle::GetSharedInstance().GetImageSkiaNamed(resource_id));
+  if (resource_id) {
+    button->SetImage(
+        views::CustomButton::STATE_NORMAL,
+        ui::ResourceBundle::GetSharedInstance().GetImageSkiaNamed(resource_id));
+  }
   button->set_tag(page_index);
   buttons_->AddChildView(button);
 }
 
 gfx::Size ContentsSwitcherView::GetPreferredSize() const {
   return gfx::Size(buttons_->GetPreferredSize().width(), kPreferredHeight);
 }
 
 void ContentsSwitcherView::Layout() {
   gfx::Rect rect(GetContentsBounds());
 
   // Makes |buttons_| horizontally center and vertically fill.
   gfx::Size buttons_size(buttons_->GetPreferredSize());
   gfx::Rect buttons_bounds(rect.CenterPoint().x() - buttons_size.width() / 2,
                            rect.y(),
                            buttons_size.width(),
                            rect.height());
   buttons_->SetBoundsRect(gfx::IntersectRects(rect, buttons_bounds));
 }
 
 void ContentsSwitcherView::ButtonPressed(views::Button* sender,
                                          const ui::Event& event) {
   contents_view_->SetActivePage(sender->tag());
 }
 
 }  // namespace app_list