Add KVO compliant title property to CWVWebView.

ios/web_view/test/chrome_web_view_kvo_inttest.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 <ChromeWebView/ChromeWebView.h>
 #import <Foundation/Foundation.h>
 
 #import "base/mac/scoped_nsobject.h"
-#import "ios/web_view/test/boolean_observer.h"
+#include "base/strings/stringprintf.h"
+#import "base/strings/sys_string_conversions.h"
 #import "ios/web_view/test/chrome_web_view_test.h"
+#import "ios/web_view/test/observers/boolean_observer.h"
+#import "ios/web_view/test/observers/string_observer.h"
 #import "ios/web_view/test/web_view_interaction_test_util.h"
 #import "net/base/mac/url_conversions.h"
 #include "testing/gtest_mac.h"
 #include "url/gurl.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 // Tests that the KVO compliant properties of CWVWebView correctly report
@@ skipping 65 matching lines @@
   EXPECT_TRUE([back_observer.lastValue boolValue]);
   EXPECT_FALSE([forward_observer.lastValue boolValue]);
 
   // Navigate back to page 2.
   [web_view_ goBack];
   WaitForPageLoadCompletion(web_view_);
   EXPECT_TRUE([back_observer.lastValue boolValue]);
   EXPECT_TRUE([forward_observer.lastValue boolValue]);
 }
 
+// Tests that CWVWebView correctly reports current |title|.
+TEST_F(ChromeWebViewKvoTest, Title) {
+  StringObserver* observer = [[StringObserver alloc] init];
+  [observer setObservedObject:web_view_ keyPath:@"title"];
+
+  NSString* page_2_title = @"Page 2";
+  GURL page_2_url =
+      GetUrlForPageWithTitle(base::SysNSStringToUTF8(page_2_title));
+
+  NSString* page_1_title = @"Page 1";
+  std::string page_1_html = base::StringPrintf(
+      "<a id='link_1' href='%s'>Link 1</a>", page_2_url.spec().c_str());
+  GURL page_1_url = GetUrlForPageWithTitleAndBody(
+      base::SysNSStringToUTF8(page_1_title), page_1_html);
+
+  LoadUrl(web_view_, net::NSURLWithGURL(page_1_url));
+  EXPECT_NSEQ(page_1_title, observer.lastValue);
+
+  // Navigate to page 2.
+  EXPECT_TRUE(test::TapChromeWebViewElementWithId(web_view_, @"link_1"));
+  WaitForPageLoadCompletion(web_view_);
+  EXPECT_NSEQ(page_2_title, observer.lastValue);
+
+  // Navigate back to page 1.
+  [web_view_ goBack];
+  WaitForPageLoadCompletion(web_view_);
+  EXPECT_NSEQ(page_1_title, observer.lastValue);
+}
+
 }  // namespace ios_web_view