Add support for chrome.app.window.create() to app_shell

apps/apps_client.h

Index: apps/apps_client.h
diff --git a/apps/apps_client.h b/apps/apps_client.h
index f67aad679c7f3b1af3035e7e4d1ccb0999735722..bd5474c9438ce40bb76305e89ccc09141a617645 100644
--- a/apps/apps_client.h
+++ b/apps/apps_client.h
@@ -17,6 +17,8 @@ class Extension;
 
 namespace apps {
 
+class AppWindow;
+
 // Sets up global state for the apps system. Should be Set() once in each
 // process. This should be implemented by the client of the apps system.
 class AppsClient {
@@ -29,6 +31,17 @@ class AppsClient {
   virtual bool CheckAppLaunch(content::BrowserContext* context,
                               const extensions::Extension* extension) = 0;
 
+  // Creates a new apps::AppWindow for the app in |extension| for |context|.
+  // Caller takes ownership.
+  virtual AppWindow* CreateAppWindow(
+      content::BrowserContext* context,
+      const extensions::Extension* extension) = 0;
+
+  // Tells the embedding application to stay running. The application may close
+  // after a matching number of calls to EndKeepAlive() are made.

[miket_OOO, 2014/02/21 18:25:38]

Nit: if the keepalive logic is a counter rather than a boolean, I wonder whether
it'd be clearer to name it accordingly, like "IncrementKeepAliveCount()."
Ideally the documentation would be optional because the method name is so clear.

Again, it's a nit. I'm not sure someone would reasonably expect a single
End...() call to work after two Start() calls, at least not without reading the
documentation. So I can see it going either way.

[James Cook, 2014/02/22 00:11:17]

The name is bad, but I prefer to have the client interface method name match the
implementation name in Chrome.  I think we should rename it everywhere.  Filed
crbug.com/345918 to do that in another CL.

+  virtual void StartKeepAlive() = 0;
+  virtual void EndKeepAlive() = 0;
+
   // Return the apps client.
   static AppsClient* Get();