[ios clean] Refactors ToolsMenu and Tabs presentation

ios/clean/chrome/browser/ui/animators/zoom_transition_controller.h

+// Copyright 2017 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_CLEAN_CHROME_BROWSER_UI_ANIMATORS_ZOOM_TRANSITION_CONTROLLER_H_

[sczs, 2017/06/22 21:46:35]

I wasn't sure in which group TransitionControllers should live. This one lives
here ,but the other one is at the ToolsMenu group since its specific to it. I
tried different locations (even creating a new group) before ending up with this
so I'm more than happy to get your thought on this. 

[marq (ping after 24h), 2017/06/23 09:18:49]

How about we have chrome/browser/ui/transitions/, which holds the transition
controllers, and then have animators/ and presenters/ as subdirectories of
transitions/?

But I'd ask that you land this as-is, and then move things around in another CL.

[sczs, 2017/06/23 14:50:20]

I like that idea. 
As you suggested I'll make those changes in another CL.

+#define IOS_CLEAN_CHROME_BROWSER_UI_ANIMATORS_ZOOM_TRANSITION_CONTROLLER_H_
+
+#import <UIKit/UIKit.h>
+
+// Transition delegate object that conforms to the
+// UIViewControllerTransitioningDelegate protocol and provides the VC

[lpromero, 2017/06/23 15:42:51]

"provides the VC": we actually don't know who is using the delegate, IIUC the
UIKit API?
What about just:
// Transition delegate object that conforms to the
// UIViewControllerTransitioningDelegate protocol and provides a ZoomAnimator as
animator.

[sczs, 2017/06/23 15:52:35]

That's actually true, will update this on the follow up CL.  

+// with a ZoomAnimator as animator for transitions.
+@interface ZoomTransitionController
+    : NSObject<UIViewControllerTransitioningDelegate>
+
+// Optional object that can be passed into the animator to identify a specific
+// location. For example, an object in a table or collection view might have
+// its index path passed in so the delegate can map that to a screen location.
+@property(nonatomic, copy) NSObject* presentationKey;
+@end
+
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_ANIMATORS_ZOOM_TRANSITION_CONTROLLER_H_