Create an interactive site-per-process browsertest class and move DocumentHasFocus there.

content/public/test/browser_test_utils.h

Index: content/public/test/browser_test_utils.h
diff --git a/content/public/test/browser_test_utils.h b/content/public/test/browser_test_utils.h
index a07ed26205bb054dbabac92d274ea4a7bf4134f9..7363dd95fbff8a36aa6d18b77e6a225d9c432319 100644
--- a/content/public/test/browser_test_utils.h
+++ b/content/public/test/browser_test_utils.h
@@ -235,6 +235,10 @@ bool FrameMatchesName(const std::string& name, RenderFrameHost* frame);
 bool FrameIsChildOfMainFrame(RenderFrameHost* frame);
 bool FrameHasSourceUrl(const GURL& url, RenderFrameHost* frame);
 
+// Finds the child frame at the specified |index| for |frame| and returns its
+// RenderFrameHost.  Returns nullptr if such child frame does not exist.
+RenderFrameHost* ChildFrameAt(RenderFrameHost* frame, size_t index);

[alexmos, 2016/04/05 16:16:56]

I thought this might be useful more generally in place of FTN's child_at() for
chrome/ tests, but I could also make this a helper inside
site_per_process_interactive_browsertest.cc.

[nasko, 2016/04/08 18:29:20]

How would that work without access to the FrameTreeNodes though? If it can work,
let's put it in the interactive tests file for now. We can put it back here if
we have more usage in the future.

[alexmos, 2016/04/11 18:37:29]

Actually, sorry, I misspoke -- I can't put it in
site_per_process_interactive_browsertest.cc, since that doesn't have access to
FrameTreeNodes.  (If I could, there would be no need for this helper. :) )  On
the other hand, browser_test_utils.cc does have access to content internal
stuff.

This is just a shorthand for getting access to subframe RFH via FTNs as opposed
to having to search for subframes by name or URL using FrameMatchingPredicate in
chrome/ tests -- for example, see OriginReplicationAllowsAccessToStorage, which
I've also now converted to use this helper.  (So with this and the second CL, it
will be used by three tests.)  Are you ok keeping it in browser_test_utils.cc?

[nasko, 2016/04/11 21:56:45]

I find the matching by name is a good way to avoid exposing more public APIs
outside of content/, but I think it is fine for this case, since it is test only
code.

+
 // Executes the WebUI resource test runner injecting each resource ID in
 // |js_resource_ids| prior to executing the tests.
 //