Add deprecation warning banner to App Launcher on Mac.

ui/app_list/app_list_view_delegate.h

Index: ui/app_list/app_list_view_delegate.h
diff --git a/ui/app_list/app_list_view_delegate.h b/ui/app_list/app_list_view_delegate.h
index 69462e78e42e6304b9d44d3980fc00fd878a0535..625463381a767153ad5571d5c03b1a03e8c77aa1 100644
--- a/ui/app_list/app_list_view_delegate.h
+++ b/ui/app_list/app_list_view_delegate.h
@@ -165,6 +165,18 @@ class APP_LIST_EXPORT AppListViewDelegate {
   // Adds/removes an observer for profile changes.
   virtual void AddObserver(AppListViewDelegateObserver* observer) {}
   virtual void RemoveObserver(AppListViewDelegateObserver* observer) {}
+
+#if !defined(OS_CHROMEOS)
+  // Methods to retrieve properties of the message displayed on the app launcher
+  // above the apps grid.
+  virtual base::string16 GetMessageTitle() const;

[Matt Giuca, 2016/03/22 03:56:15]

Also I think these should be =0 and add overrides in AppListTestViewDelegate.
(thoughts?)

[tapted, 2016/03/22 04:19:50]

There's precedent for impure virtuals already for the observers above. I don't
think there's any upside to making these pure - just makes the CL bigger and the
#ifdefs more confusing.

[Matt Giuca, 2016/03/22 04:23:43]

That isn't precedent in my mind -- observers should always be impure. Do these
methods make sense if they are not implemented? If not, they should be pure.

Not that it matters; this code will be short lived. Happy to leave it as-is.

+  virtual base::string16 GetMessageText() const;

[Matt Giuca, 2016/03/22 03:28:06]

// Returns the message text (with the placeholder symbol removed). |offset| is
set to the index where the placeholder was in the string.
virtual base::string16 GetMessageText(size_t* offset) const;

See my comment in app_list_view_controller.mm.

[tapted, 2016/03/22 04:58:14]

Acknowledged.

+  virtual base::string16 GetAppsShortcutName() const;
+  virtual base::string16 GetLearnMoreText() const;
+  virtual base::string16 GetLearnMoreLink() const;
+  virtual gfx::ImageSkia* GetAppsIcon() const;
+  virtual void OpenLearnMoreLink();
+#endif
 };
 
 }  // namespace app_list