Add a "started" protected property to BrowserCoordinator.

ios/clean/chrome/browser/browser_coordinator+internal.h

 // Copyright 2016 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.
 
 // ======                        New Architecture                         =====
 // =         This code is only used in the new iOS Chrome architecture.       =
 // ============================================================================
 
 #ifndef IOS_CHROME_BROWSER_BROWSER_COORDINATOR_INTERNAL_H_
 #define IOS_CHROME_BROWSER_BROWSER_COORDINATOR_INTERNAL_H_
@@ skipping 19 matching lines @@
 // controller through this property.
 @property(nonatomic, readonly) UIViewController* viewController;
 
 // The child coordinators of this coordinator. To add or remove from this set,
 // use the -addChildCoordinator: and -removeChildCoordinator: methods.
 @property(nonatomic, readonly) NSSet<BrowserCoordinator*>* children;
 
 // The coordinator that added this coordinator as a child, if any.
 @property(nonatomic, readonly) BrowserCoordinator* parentCoordinator;
 
+// YES if the receiver has been started; NO (the default) otherwise. Stopping
+// the receiver resets this property to NO.
+@property(nonatomic, readonly) BOOL started;
+
 // YES if the receiver is acting as an overlay coordinator; NO (the default)
 // otherwise.
 @property(nonatomic, readonly) BOOL overlaying;
 
 // The coordinator (if any) in the coordinator hierarchy (starting with
 // the receiver) that is overlaying. If the receiver isn't overlaying,
 // it recursively asks its children.
 @property(nonatomic, readonly) BrowserCoordinator* overlayCoordinator;
 
 // Adds |coordinator| as a child, taking ownership of it, setting the receiver's
@@ skipping 31 matching lines @@
 // nothing happens.
 - (void)addOverlayCoordinator:(BrowserCoordinator*)overlayCoordinator;
 
 // Removes the current overlay coordinator (if any) as a child from its
 // parent.
 - (void)removeOverlayCoordinator;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_BROWSER_COORDINATOR_INTERNAL_H_