Add WebWidgetTestProxy.

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index 27f71b3bc552e5e10c871e9a0b774a5ea8bfee01..fbe826b77897d20f9b31d485378bc0f27983c53a 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -127,6 +127,16 @@ class CONTENT_EXPORT RenderWidget
                                       CompositorDependencies* compositor_deps,
                                       blink::WebLocalFrame* frame);
 
+  using CreateRenderWidgetFunction =
+      RenderWidget* (*)(CompositorDependencies*,
+                        blink::WebPopupType,
+                        const blink::WebScreenInfo&,
+                        bool,
+                        bool,
+                        bool);
+  static void InstallCreateHook(
+      CreateRenderWidgetFunction create_render_widget);

[Łukasz Anforowicz, 2016/08/02 20:38:12]

Perhaps we might want to indicate (with a comment?) that this method is meant to
be used only from test code.  Maybe we can use something similar to a comment
present in render_view_impl.h: // Used by content_layouttest_support to hook
into the creation of RenderViewImpls^H^H^HRenderWidgets.

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

Done.

+
   // Closes a RenderWidget that was created by |CreateForFrame|.
   // TODO(avi): De-virtualize this once RenderViewImpl has-a RenderWidget.
   // https://crbug.com/545684