Add WebWidgetTestProxy.

third_party/WebKit/public/web/WebWidget.h

Index: third_party/WebKit/public/web/WebWidget.h
diff --git a/third_party/WebKit/public/web/WebWidget.h b/third_party/WebKit/public/web/WebWidget.h
index bc0a6faeadee75a26c1916d92d571baf15aba835..fa3c4fab267f362e56a6e28ebf5a7e6cbe5b5d96 100644
--- a/third_party/WebKit/public/web/WebWidget.h
+++ b/third_party/WebKit/public/web/WebWidget.h
@@ -208,6 +208,10 @@ public:
 
     // Returns true if the WebWidget created is of type WebView.
     virtual bool isWebView() const { return false; }
+
+    // Returns true if the WebWidget created is of type WebFrameWidget.
+    virtual bool isWebFrameWidget() const { return false; }

[Łukasz Anforowicz, 2016/08/02 20:38:13]

I think I am okay with having a new method to be used only from tests / only for
CHECK.  I am worried that the new method looks to be part of the generic API
surface of WebWidget and in the future product code can start to make decisions
based on the new API (or would that be okay?).

2 options I can think of:
- Maybe add ForTesting suffix to the name? (I don't like this option)
- Maybe remove isWebFrameWidget() method and replace it with
assertIsWebFrameWidget() method - this way the method is less likely to be
abused in product code's conditions / decision making.

[lfg, 2016/08/02 22:27:21]

I'm not convinced that this would be bad.
I also don't like this.
I'm ok with this, but I prefer to leave isWebFrameWidget() in the API, since I'm
not convinced anything bad can come out of it's usage. It's there mostly for
safety, and the performance impact should be small.

[Łukasz Anforowicz, 2016/08/02 22:35:23]

Okay - sgtm, if Blink owners approve.

+
     // Returns true if the WebWidget created is of type WebPagePopup.
     virtual bool isPagePopup() const { return false; }