[ios] Create FindInPageManager in CRWWebController

Creates an instance of FindInPageManager for every WebState.

Bug: 919685
Change-Id: I17f3fe7f10268c586e7aca2dbe1f0a5e3d65cc8f
Reviewed-on: https://chromium-review.googlesource.com/c/1450624
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628581}

ios/web/web_state/ui/BUILD.gn

@@ -14,6 +14,7 @@ source_set("ui") {
     "//base",
     "//ios/net",
     "//ios/web:core",
+    "//ios/web/find_in_page",
     "//ios/web/interstitials",
     "//ios/web/navigation",
     "//ios/web/navigation:core",

ios/web/web_state/ui/crw_web_controller.mm

@@ -40,6 +40,7 @@
 #include "base/values.h"
 #include "crypto/symmetric_key.h"
 #import "ios/net/http_response_headers_util.h"
+#import "ios/web/find_in_page/find_in_page_manager_impl.h"
 #include "ios/web/history_state_util.h"
 #import "ios/web/interstitials/web_interstitial_impl.h"
 #import "ios/web/navigation/crw_navigation_item_holder.h"
@@ -958,6 +959,7 @@ GURL URLEscapedForHistory(const GURL& url) {
         std::make_unique<CertVerificationErrorsCacheType>(kMaxCertErrorsCount);
     _navigationStates = [[CRWWKNavigationStates alloc] init];
     web::WebFramesManagerImpl::CreateForWebState(_webStateImpl);
+    web::FindInPageManagerImpl::CreateForWebState(_webStateImpl);
     [[NSNotificationCenter defaultCenter]
         addObserver:self
            selector:@selector(orientationDidChange)