[ios] Moves the Find in Page APIs into FindTabHelper.

ios/chrome/browser/find_in_page/find_tab_helper.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_CHROME_BROWSER_FIND_IN_PAGE_FIND_TAB_HELPER_H_
 #define IOS_CHROME_BROWSER_FIND_IN_PAGE_FIND_TAB_HELPER_H_
 
+#include <Foundation/Foundation.h>
+
+#include "base/ios/block_types.h"
+#import "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "ios/web/public/web_state/web_state_observer.h"
 #import "ios/web/public/web_state/web_state_user_data.h"
 
 @class FindInPageController;
 @protocol FindInPageControllerDelegate;
+@class FindInPageModel;
+
+typedef void (^FindInPageCompletionBlock)(FindInPageModel*);
 
 // Adds support for the "Find in page" feature.
 class FindTabHelper : public web::WebStateObserver,
                       public web::WebStateUserData<FindTabHelper> {
  public:
+  enum FindDirection {
+    FORWARD,
+    REVERSE,
+  };
+
   // Creates a FindTabHelper and attaches it to the given |web_state|.
   // |controller_delegate| can be nil.
   static void CreateForWebState(
       web::WebState* web_state,
       id<FindInPageControllerDelegate> controller_delegate);
 
-  // Returns the find in page controller.
-  FindInPageController* GetController();
+  // Starts an asynchronous Find operation that will call the given completion
+  // handler with results.  Always searches in the FORWARD direction.
+  void StartFinding(NSString* search_string,
+                    FindInPageCompletionBlock completion);
+
+  // Runs an asynchronous Find operation that will call the given completion
+  // handler with results.  Uses the previously remembered search string and
+  // searches in the given |direction|.

[stkhapugin, 2017/03/14 14:06:15]

Specify how this and other methods can be called wrt completion blocks being not
called yet. 
nit: Worth saying that it will highlight the next/prev result (it's not super
clear from the comment imo).

[rohitrao (ping after 24h), 2017/03/14 14:50:53]

Added a note about highlighting to the method comment.

I don't fully understand what happens if you call this method twice in a row
before the completion handler runs.  Leaving this out for now, but I'll come
back to it when I convert these calls to take base::Callbacks instead of blocks.

+  void ContinueFinding(FindDirection direction,
+                       FindInPageCompletionBlock completion);
+
+  // Stops any running find operations and runs the given completion block.
+  void StopFinding(ProceduralBlock completion);
+
+  // Returns the FindInPageModel that contains the latest find results.
+  FindInPageModel* GetFindResult() const;
+
+  // Returns true if the currently loaded page supports Find in Page.
+  bool CurrentPageSupportsFindInPage() const;
+
+  // Returns true if the Find in Page UI is currently visible.
+  bool IsFindUIActive() const;
+
+  // Marks the Find in Page UI as visible or not.  This method does not directly
+  // show or hide the UI.  It simply acts as a marker for whether or not the UI
+  // is visible.
+  void SetFindUIActive(bool active);
+
+  // Saves the current find text to persistent storage.
+  void PersistSearchTerm();
+
+  // Restores the current find text from persistent storage.
+  void RestoreSearchTerm();
 
  private:
+  friend class FindTabHelperTest;
+
   FindTabHelper(web::WebState* web_state,
                 id<FindInPageControllerDelegate> controller_delegate);
   ~FindTabHelper() override;
 
   // web::WebStateObserver.
   void NavigationItemCommitted(
       const web::LoadCommittedDetails& load_details) override;
   void WebStateDestroyed() override;
 
   // The ObjC find in page controller.
-  FindInPageController* controller_;
+  base::scoped_nsobject<FindInPageController> controller_;
 
   DISALLOW_COPY_AND_ASSIGN(FindTabHelper);
 };
 
 #endif  // IOS_CHROME_BROWSER_FIND_IN_PAGE_FIND_TAB_HELPER_H_