Remove CWV class and move setting User Agent to CWVWebViewConfiguration.

ios/web_view/public/cwv_web_view.h

Index: ios/web_view/public/cwv_web_view.h
diff --git a/ios/web_view/public/cwv_web_view.h b/ios/web_view/public/cwv_web_view.h
index 1989c9e775fe69e0ea21a8873917656713125ff6..7ff778595b8c686793f7da0665459a2a537eec4e 100644
--- a/ios/web_view/public/cwv_web_view.h
+++ b/ios/web_view/public/cwv_web_view.h
@@ -54,6 +54,14 @@ CWV_EXPORT
 // is reset to 0.0.
 @property(nonatomic, readonly) double estimatedProgress;
 
+// Customizes the User Agent string. It should be of the format "product/1.0".
+// NOTE: It is recommended to set |product| before initializing any web views.
+//
+// Setting |product| is only guaranteed to affect web views which have not yet

[Eugene But (OOO till 7-30), 2017/04/11 17:52:42]

Do you want to document how calling this API will actually affect final UA
string?

[michaeldo, 2017/04/11 21:57:03]

I added a note that |product| is inserted into the UA string. I don't know if
it's helpful to show a full example here as it will change and the documentation
will likely be out of date. WDYT?

[Eugene But (OOO till 7-30), 2017/04/12 00:46:17]

I think it is helpful to explain why clients would want to call this method and
what will happen if they don't call it (I assume that UA will look silly in this
case).

[Eugene But (OOO till 7-30), 2017/04/12 17:48:27]

Please take a look at this comment.

[michaeldo, 2017/04/12 18:22:55]

I've added example UA.

+// been initialized. However, exisiting web views could also be affected
+// depending upon their internal state.
++ (void)setUserAgentProduct:(NSString*)product;
+
 // |configuration| must not be null
 - (instancetype)initWithFrame:(CGRect)frame
                 configuration:(CWVWebViewConfiguration*)configuration