Remove CWV class and move setting User Agent to CWVWebViewConfiguration.

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 424abf3765b4357589ca2e8d3eaa63fbd93d365e..f722d4a669e0914a1e0cd1dc72a6d944b7d37ad2 100644
--- a/ios/web_view/public/cwv_web_view_configuration.h
+++ b/ios/web_view/public/cwv_web_view_configuration.h
@@ -23,6 +23,11 @@ CWV_EXPORT
 
 - (instancetype)init NS_UNAVAILABLE;
 
+// Customizes the User Agent string used by web views. It should be of the
+// format "product/1.0". NOTE: This must be called before any

[Eugene But (OOO till 7-30), 2017/04/04 21:50:26]

This is pretty strict requirement. Is it temporary? Or so, please add a TODO. I
think we should avoid API that "must be called" before anything else.

[michaeldo, 2017/04/07 22:31:35]

Moved to CWVWebView as static method per discussion. Added better comment there
as well.

+// CWVWebViewConfiguration is initialized.
++ (void)setUserAgentProductName:(NSString*)userAgent;
+
 // The user content controller to associate with web views created using this
 // configuration.
 @property(nonatomic, readonly) CWVUserContentController* userContentController;