Add KVO compliant title property to CWVWebView.

ios/web_view/test/chrome_web_view_kvo_inttest.mm

Index: ios/web_view/test/chrome_web_view_kvo_inttest.mm
diff --git a/ios/web_view/test/chrome_web_view_kvo_inttest.mm b/ios/web_view/test/chrome_web_view_kvo_inttest.mm
index 4425439ebad39f05ea02b05e8a6aebc112f732cf..319abfc098279abc4176903e793b6077e45187d3 100644
--- a/ios/web_view/test/chrome_web_view_kvo_inttest.mm
+++ b/ios/web_view/test/chrome_web_view_kvo_inttest.mm
@@ -6,8 +6,10 @@
 #import <Foundation/Foundation.h>
 
 #import "base/mac/scoped_nsobject.h"
-#import "ios/web_view/test/boolean_observer.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"

[Eugene But (OOO till 7-30), 2017/05/25 17:43:03]

Do we actually need 2 different observers for BOOL and NSString? From KVO
perspective both are just id. Also implementation of subclasses differs only by
type, which seems to be redundant for dynamically types language.

[michaeldo, 2017/05/26 14:59:01]

It's true that they are not required as the one that uses id would work fine.
However there are lots of places that access the value in these tests and I
think it is better to have the specific classes for common use case types (like
here with strings and bool). I don't think we would want subclasses for every
class type, but I personally think it's clearer with the specific classes in
these cases.

[Eugene But (OOO till 7-30), 2017/05/31 22:10:00]

Objective-C has one KVO callback for all types, because dynamic typing is a
feature, so we could also take advantage of that. If we add classes for BOOL and
String, then we'll have to add a class for Number and URL. What would be the
advantage of having 5 classes instead of 1 class?

[Eugene But (OOO till 7-30), 2017/06/01 15:53:54]

Please look at this comment

 #import "ios/web_view/test/web_view_interaction_test_util.h"
 #import "net/base/mac/url_conversions.h"
 #include "testing/gtest_mac.h"
@@ -93,4 +95,33 @@ TEST_F(ChromeWebViewKvoTest, CanGoBackForward) {
   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 =
+      "<a id='link_1' href='" + page_2_url.spec() + "'>Link 1</a>";

[Eugene But (OOO till 7-30), 2017/05/25 17:43:03]

Please se StringPrint instead of +

[michaeldo, 2017/05/26 14:59:01]

Done.

+  GURL page_1_url = GetUrlForPageWithTitleAndBody(
+      base::SysNSStringToUTF8(page_1_title), page_1_html);
+
+  LoadUrl(web_view_, net::NSURLWithGURL(page_1_url));
+  EXPECT_NSEQ(observer.lastValue, page_1_title);
+
+  // Navigate to page 2.
+  EXPECT_TRUE(test::TapChromeWebViewElementWithId(web_view_, @"link_1"));
+  WaitForPageLoadCompletion(web_view_);
+  EXPECT_NSEQ(observer.lastValue, page_2_title);

[Eugene But (OOO till 7-30), 2017/05/25 17:43:03]

EXPECT_NSEQ takes first argument as expected value and second as actual

[michaeldo, 2017/05/26 14:59:01]

Done.

+
+  // Navigate back to page 1.
+  [web_view_ goBack];
+  WaitForPageLoadCompletion(web_view_);
+  EXPECT_NSEQ(observer.lastValue, page_1_title);
+}
+
 }  // namespace ios_web_view