Add KVO compliant title property to CWVWebView.

ios/web_view/test/observers/BUILD.gn

Index: ios/web_view/test/observers/BUILD.gn
diff --git a/ios/web_view/test/observers/BUILD.gn b/ios/web_view/test/observers/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..1a43f600bdc4d1a78bc2f4f10a07e23ac79942f1
--- /dev/null
+++ b/ios/web_view/test/observers/BUILD.gn
@@ -0,0 +1,17 @@
+# 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.
+
+source_set("observers") {
+  testonly = true
+  sources = [
+    "boolean_observer.h",
+    "boolean_observer.mm",
+    "observer.h",
+    "observer.mm",
+    "string_observer.h",
+    "string_observer.mm",
+  ]
+
+  configs += [ "//build/config/compiler:enable_arc" ]
+}