Add protocol APIs to CommandDispatcher.

ios/shared/chrome/browser/ui/commands/command_dispatcher.h

Index: ios/shared/chrome/browser/ui/commands/command_dispatcher.h
diff --git a/ios/shared/chrome/browser/ui/commands/command_dispatcher.h b/ios/shared/chrome/browser/ui/commands/command_dispatcher.h
index eaf784fb1221b1aff2e247be769e0ba09973fe7a..f264d35254a3ed16ceb28a6bccbdd980fe762f1b 100644
--- a/ios/shared/chrome/browser/ui/commands/command_dispatcher.h
+++ b/ios/shared/chrome/browser/ui/commands/command_dispatcher.h
@@ -16,9 +16,19 @@
 // |selector|.
 - (void)startDispatchingToTarget:(id)target forSelector:(SEL)selector;
 
+// Registers the given |target| to receive forwarded messages for the methods of
+// the given |protocol|. Only required instance methods are registered. The
+// other definitions in the protocol are ignored.
+- (void)startDispatchingToTarget:(id)target forProtocol:(Protocol*)protocol;
+
 // Removes forwarding registration for the given |selector|.
 - (void)stopDispatchingForSelector:(SEL)selector;
 
+// Removes forwarding registration for the given |selector|. Only dispatching to
+// required instance methods is removed. The other definitions in the protocol
+// are ignored.
+- (void)stopDispatchingForProtocol:(Protocol*)protocol;
+
 // Removes all forwarding registrations for the given |target|.
 - (void)stopDispatchingToTarget:(id)target;