Annotates functions returning retained objects.

ios/web/net/clients/crw_js_injection_network_client_unittest.mm

Index: ios/web/net/clients/crw_js_injection_network_client_unittest.mm
diff --git a/ios/web/net/clients/crw_js_injection_network_client_unittest.mm b/ios/web/net/clients/crw_js_injection_network_client_unittest.mm
index b5353d5dc850920a0bff2287dfabf9143cf81972..19958204aede0cc335fdb575f04cec3351ed9a7c 100644
--- a/ios/web/net/clients/crw_js_injection_network_client_unittest.mm
+++ b/ios/web/net/clients/crw_js_injection_network_client_unittest.mm
@@ -111,7 +111,8 @@ class CRWJSInjectionNetworkClientTest : public testing::Test {
  protected:
   // Returns a CRNHTTPURLResponse. If |include_content_length|, header includes
   // Content-Length set to the length of test_data_.
-  CRNHTTPURLResponse* CreateTestResponse(BOOL include_content_length);
+  CRNHTTPURLResponse* CreateTestResponse(BOOL include_content_length)
+      NS_RETURNS_RETAINED;
 
   // Returns number of times an injected cr_web script tag is found in the
   // underlying client's loaded data. Script tag should immediately follow
@@ -130,7 +131,7 @@ class CRWJSInjectionNetworkClientTest : public testing::Test {
 };
 
 CRNHTTPURLResponse* CRWJSInjectionNetworkClientTest::CreateTestResponse(
-    BOOL include_content_length) {
+    BOOL include_content_length) NS_RETURNS_RETAINED {

[Eugene But (OOO till 7-30), 2016/08/16 16:45:48]

Is it necessary to annotate in both interface and implementation?

[stkhapugin, 2016/08/16 16:51:49]

Actually this annotation only makes a difference in headers (as it only changes
behavior across arc/mrr boundaries), but we don't really have any guideline for
this, so I marked the ones in implementation files as well. 

[Eugene But (OOO till 7-30), 2016/08/16 17:02:31]

If |NS_RETURNS_RETAINED| in implementation does not add any value (and seems
like it does not) I think we should not clutter our code with unnecessary stuff.
Do you see any good reason for adding these annotations (except that Style Guide
is silent on this)?

   NSMutableDictionary *headers = [NSMutableDictionary
       dictionaryWithDictionary:@{ @"Content-Type" : @"text/html" }];
   if (include_content_length) {