Quit the message loop by default in ShellConnectionLost when ApplicationRunner is used

mojo/shell/public/cpp/shell_client.h

Index: mojo/shell/public/cpp/shell_client.h
diff --git a/mojo/shell/public/cpp/shell_client.h b/mojo/shell/public/cpp/shell_client.h
index d6fca12bed0ba4dc2a8fc5cb31bd86c4dced6765..aff1aac40ed5797f7c6b66462d47ccb49115eec6 100644
--- a/mojo/shell/public/cpp/shell_client.h
+++ b/mojo/shell/public/cpp/shell_client.h
@@ -43,8 +43,13 @@ class ShellClient {
 
   // Called when ShellConnection's ShellClient binding (i.e. the pipe the
   // Mojo Shell has to talk to us over) is closed. A shell client may use this
-  // as a signal to terminate.
-  virtual void ShellConnectionLost();
+  // as a signal to terminate. Return true from this method to tell the
+  // ShellConnection to run its connection lost closure if it has one, false to
+  // prevent it from being run. The default implementation returns true.
+  // When used in conjunction with ApplicationRunner, returning true here quits
+  // the message loop created by ApplicationRunner, which results in the app
+  // quitting.
+  virtual bool ShellConnectionLost();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ShellClient);