Add a URL param to indicate group selection in Instant field trial.

chrome/browser/search_engines/template_url_service.h

Index: chrome/browser/search_engines/template_url_service.h
diff --git a/chrome/browser/search_engines/template_url_service.h b/chrome/browser/search_engines/template_url_service.h
index 602c4656c82246a2ab5acf94cc2f416efa23ceca..2da10e54ff34cd513342d127e2339d8d9abed13c 100644
--- a/chrome/browser/search_engines/template_url_service.h
+++ b/chrome/browser/search_engines/template_url_service.h
@@ -91,12 +91,13 @@ class TemplateURLService : public WebDataServiceConsumer,
 
   // Returns the search url for t_url.  Returns an empty GURL if t_url has no
   // url().
-  static GURL GenerateSearchURL(const TemplateURL* t_url);
+  static GURL GenerateSearchURL(Profile* profile, const TemplateURL* t_url);
 
   // Just like GenerateSearchURL except that it takes SearchTermsData to supply
   // the data for some search terms. Most of the time GenerateSearchURL should
   // be called.
   static GURL GenerateSearchURLUsingTermsData(
+      Profile* profile,

[sky, 2011/08/08 23:37:23]

This method shouldn't take a profile, it's intended to be invoked from any
thread. If you say you'll just supply NULL, that doesn't sit well with me as
it's all to easy to get it wrong and the signature implies you should pass in a
Profile.

[sreeram, 2011/08/09 16:24:01]

I only supply NULL where the caller strips away the params immediately (and
where passing a real Profile* would require jumping through a lot more hoops).
For example, see the calls in search_host_to_urls_map.cc.

In places where a Profile is readily available, I do supply it. For example, see
the calls in template_url_prepopulate_data_unittest.cc. It turns out that all
such cases are in test code, where the tests would pass just fine even if I
passed NULL.

So, if you prefer, I can remove the Profile* parameter from the
GenerateSearchURL*() methods, which would mean that I would then pass NULL
instead on line 214 in template_url_service.cc, i.e., where
GenerateSearchURLUsingTermsData() calls ReplaceSearchTermsUsingTermsData().
Would you prefer that?

       const TemplateURL* t_url,
       const SearchTermsData& search_terms_data);