[ios] Adds the LogoVendor protocol.

ios/public/provider/chrome/browser/ui/logo_vendor.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.
+
+#ifndef IOS_PUBLIC_PROVIDER_CHROME_BROWSER_UI_LOGO_VENDOR_H_
+#define IOS_PUBLIC_PROVIDER_CHROME_BROWSER_UI_LOGO_VENDOR_H_
+
+#import "ios/public/provider/chrome/browser/voice/logo_animation_controller.h"
+
+@class UIView;
+
+// Defines a controller whose view contains a doodle or search engine logo.
+@protocol LogoVendor<LogoAnimationControllerOwnerOwner, NSObject>

[sdefresne, 2016/10/28 11:27:06]

Do you need to inherit from NSObject protocol? I think this is only required if
you invoke respondsToSelect: on id<LogoVendor>.

[rohitrao (ping after 24h), 2016/10/28 11:31:58]

I think I can get away without it, but I'd like to keep it because we store and
use objects as id<LogoVendor>, which makes me want them to act like NSObjects.

+
+// View that shows a doodle or a search engine logo.
+@property(nonatomic, readonly) UIView* view;
+
+// Whether or not the logo should be shown.  Defaults to YES.
+@property(nonatomic, assign, getter=isShowingLogo) BOOL showingLogo;
+
+// Checks for a new doodle.  Calling this method frequently will result in a
+// query being issued at most once per hour.
+- (void)fetchDoodle;
+
+@end
+
+#endif  // IOS_PUBLIC_PROVIDER_CHROME_BROWSER_UI_LOGO_VENDOR_H_