[content shell] change how the main render view is picked for layout tests

content/public/test/layouttest_support.h

Index: content/public/test/layouttest_support.h
diff --git a/content/public/test/layouttest_support.h b/content/public/test/layouttest_support.h
index b625d5455c17eafc30fd9b5630af81addc9c45e9..0a83b2ac51f16f867602ee7b5d34a2681d586809 100644
--- a/content/public/test/layouttest_support.h
+++ b/content/public/test/layouttest_support.h
@@ -13,11 +13,13 @@ class WebTestProxyBase;
 
 namespace content {
 
+class RenderView;
+
 // Enable injecting of a WebTestProxy between WebViews and RenderViews.
 // |callback| is invoked with a pointer to WebTestProxyBase for each created
 // WebTestProxy.
-void EnableWebTestProxyCreation(
-    const base::Callback<void(WebTestRunner::WebTestProxyBase*)>& callback);
+void EnableWebTestProxyCreation(const base::Callback<
+    void(RenderView*, WebTestRunner::WebTestProxyBase*)>& callback);
 
 }  // namespace content