Expose way to set google api key through CWVWebView class method.

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 86de8f52c87bbe10faf941d4d1f072f25e2db55a..7de1bbd5daa12b8bdf553d058808637d96ee3354 100644
--- a/ios/web_view/public/cwv_web_view.h
+++ b/ios/web_view/public/cwv_web_view.h
@@ -61,6 +61,12 @@ CWV_EXPORT
 // is reset to 0.0.
 @property(nonatomic, readonly) double estimatedProgress;
 
+// This is used by to communicate with the Translate API, among others.

[Eugene But (OOO till 7-30), 2017/03/31 18:15:14]

Could you please explain in the comments what arguments should be passed. Maybe
a link to public Google API doc, where APIKey, clientID and clientSecret are
described.

[jzw1, 2017/04/11 08:28:46]

Done.

+// This method should be called before any CWVWebViews are instantiated.

[Eugene But (OOO till 7-30), 2017/03/31 18:15:14]

"before any CWVWebViews are instantiated" or "before a page is loaded"?

[michaeldo, 2017/03/31 20:28:16]

IIRC this needs to happen before the object is instantiated.

[Hiroshi Ichikawa, 2017/04/03 05:28:16]

Should it happen even before +[CWV configureWithDelegate:]? If so, it should
also be documented.

[jzw1, 2017/04/11 08:28:46]

I'd rather not add "before CWV configureWitDelegate" since we're planning on
removing it anyways.
It's more accurate to say before page load, but I think it's important to
communicate to the user that this method should be called before everything,
hence I went with the more conservative "before instantiation".

++ (void)setGoogleAPIKey:(NSString*)googleAPIKey
+               clientID:(NSString*)clientID
+           clientSecret:(NSString*)clientSecret;
+
 // |configuration| must not be null
 - (instancetype)initWithFrame:(CGRect)frame
                 configuration:(CWVWebViewConfiguration*)configuration