Add CWVUserContentController which enables injecting JavaScripts.

ios/web_view/public/cwv_web_view_configuration.h

Index: ios/web_view/public/cwv_web_view_configuration.h
diff --git a/ios/web_view/public/cwv_web_view_configuration.h b/ios/web_view/public/cwv_web_view_configuration.h
index a2a7489b3c4cfe52c9aecddae946bd731bdc8f4d..821c5f8725bcc809e6d96c91f852c77c6e8cda91 100644
--- a/ios/web_view/public/cwv_web_view_configuration.h
+++ b/ios/web_view/public/cwv_web_view_configuration.h
@@ -7,6 +7,7 @@
 
 #import <Foundation/Foundation.h>
 
+@class CWVUserContentController;
 @class CWVWebsiteDataStore;
 
 // Configuration used for creation of a CWVWebView.
@@ -20,6 +21,9 @@
 
 - (instancetype)init NS_UNAVAILABLE;
 
+// The user content controller to associate with the web view.

[michaeldo, 2017/03/21 16:12:35]

nit: I think "the web view" seems a bit arbitrary as this is the configuration
object, not the web view itself. WDYT about:

The user content controller to associate with web views created using this
configuration.

[Hiroshi Ichikawa, 2017/03/22 04:52:53]

Done.

+@property(nonatomic, readonly) CWVUserContentController* userContentController;
+
 // YES if it is a configuration with persistent data store which stores all data
 // on disk.
 @property(readonly, getter=isPersistent) BOOL persistent;

[Eugene But (OOO till 7-30), 2017/03/21 16:47:55]

nonatomic ?

[Hiroshi Ichikawa, 2017/03/22 04:52:53]

Done.