[ios] Added API to enable/disable web usage for WebState.

ios/web/web_state/web_state_impl_unittest.mm

 // Copyright 2014 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.
 
 #include "ios/web/web_state/web_state_impl.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 264 matching lines @@
     EXPECT_TRUE(web_state_->IsLoading());
     base::test::ios::WaitUntilCondition(^bool() {
       return !web_state_->IsLoading();
     });
   }
 
   web::TestBrowserState browser_state_;
   std::unique_ptr<WebStateImpl> web_state_;
 };
 
+TEST_F(WebStateTest, WebUsageEnabled) {
+  // Default is false.
+  ASSERT_FALSE(web_state_->IsWebUsageEnabled());
+
+  web_state_->SetWebUsageEnabled(true);
+  EXPECT_TRUE(web_state_->IsWebUsageEnabled());
+  EXPECT_TRUE(web_state_->GetWebController().webUsageEnabled);
+
+  web_state_->SetWebUsageEnabled(false);
+  EXPECT_FALSE(web_state_->IsWebUsageEnabled());
+  EXPECT_FALSE(web_state_->GetWebController().webUsageEnabled);
+}
+
 TEST_F(WebStateTest, ResponseHeaders) {
   GURL real_url("http://foo.com/bar");
   GURL frame_url("http://frames-r-us.com/");
   scoped_refptr<net::HttpResponseHeaders> real_headers(HeadersFromString(
       "HTTP/1.1 200 OK\r\n"
       "Content-Type: text/html\r\n"
       "Content-Language: en\r\n"
       "X-Should-Be-Here: yep\r\n"
       "\r\n"));
   scoped_refptr<net::HttpResponseHeaders> frame_headers(HeadersFromString(
@@ skipping 281 matching lines @@
     return execution_result.get();
   });
 
   std::string string_result;
   execution_result->GetAsString(&string_result);
   EXPECT_EQ("bar", string_result);
 }
 
 }  // namespace
 }  // namespace web