[ios] Moves find-in-page code out of Tab and into FindTabHelper.

ios/chrome/browser/find_in_page/find_tab_helper.mm

+// 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.
+
+#import "ios/chrome/browser/find_in_page/find_tab_helper.h"
+
+#import "ios/chrome/browser/find_in_page/find_in_page_controller.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+DEFINE_WEB_STATE_USER_DATA_KEY(FindTabHelper);
+
+// static
+void FindTabHelper::CreateForWebState(
+    web::WebState* web_state,
+    id<FindInPageControllerDelegate> controller_delegate) {
+  DCHECK(web_state);
+  if (!FromWebState(web_state)) {
+    web_state->SetUserData(UserDataKey(),
+                           new FindTabHelper(web_state, controller_delegate));
+  }
+}
+
+FindTabHelper::FindTabHelper(
+    web::WebState* web_state,
+    id<FindInPageControllerDelegate> controller_delegate) {
+  controller_ =
+      [[FindInPageController alloc] initWithWebState:web_state
+                                            delegate:controller_delegate];
+}
+
+FindTabHelper::~FindTabHelper() {}
+
+FindInPageController* FindTabHelper::GetController() {
+  return controller_;
+}
+
+void FindTabHelper::NavigationItemCommitted(
+    const web::LoadCommittedDetails& load_details) {
+  [controller_ disableFindInPageWithCompletionHandler:nil];
+}
+
+void FindTabHelper::WebStateDestroyed() {
+  [controller_ detachFromWebState];
+}