Fixes disappearing text in Find in page toolbar in slide over.

ios/chrome/browser/find_in_page/find_in_page_controller.mm

 // Copyright 2012 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_in_page_controller.h"
 
 #import <UIKit/UIKit.h>
 #import <cmath>
 
 #include "base/ios/ios_util.h"
@@ skipping 272 matching lines @@
   } else {
     handler();
   }
 }
 
 - (void)saveSearchTerm {
   [self findPasteboard].string = [[self findInPageModel] text];
 }
 
 - (void)restoreSearchTerm {
+  // Pasteboards always return nil in background:
+  if ([[UIApplication sharedApplication] applicationState] !=
+      UIApplicationStateActive) {
+    return;
+  }
+
   NSString* term = [self findPasteboard].string;
   [[self findInPageModel] updateQuery:(term ? term : @"") matches:0];
 }
 
 - (UIPasteboard*)findPasteboard {
   return [UIPasteboard pasteboardWithName:UIPasteboardNameFind create:NO];
 }
 
 - (web::WebState*)webState {
   return _webStateObserverBridge ? _webStateObserverBridge->web_state()
@@ skipping 66 matching lines @@
 
 - (BOOL)canReleaseDOMLock {
   return NO;
 }
 
 - (void)releaseDOMLockWithCompletionHandler:(ProceduralBlock)completionHandler {
   NOTREACHED();
 }
 
 @end