[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(),

[Eugene But (OOO till 7-30), 2017/02/10 00:03:36]

nit: do you want to add braces, because block is multiline?

Style Guide is quite vague on that:

"In general, curly braces are not required for single-line statements, but they
are allowed if you like them; conditional or loop statements with complex
conditions or statements may be more readable with curly braces. Some projects
require that an if must always always have an accompanying brace."

[sdefresne, 2017/02/10 09:39:51]

Even though the style guide does not enforce this, it looks like brace on
complex if statement are more frequent in Chromium (at least my reviewer ask me
to put braces there).

[rohitrao (ping after 24h), 2017/02/10 13:52:18]

I prefer braces for all conditionals, thanks =)

+                           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];
+}