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

chrome/browser/search_engines/template_url.h

Index: chrome/browser/search_engines/template_url.h
diff --git a/chrome/browser/search_engines/template_url.h b/chrome/browser/search_engines/template_url.h
index a723530c00f0d13210ad1c9f1ffdcc6a1ce2050b..b8a81ffb0baa28ef302c215c70c51dc477288df7 100644
--- a/chrome/browser/search_engines/template_url.h
+++ b/chrome/browser/search_engines/template_url.h
@@ -16,6 +16,7 @@
 #include "googleurl/src/gurl.h"
 
 class PrefService;
+class Profile;
 class SearchTermsData;
 class TemplateURL;
 class WebDataService;
@@ -71,6 +72,7 @@ class TemplateURLRef {
   //
   // The TemplateURL is used to determine the input encoding for the term.
   std::string ReplaceSearchTerms(
+      Profile* profile,
       const TemplateURL& host,
       const string16& terms,
       int accepted_suggestion,
@@ -80,6 +82,7 @@ class TemplateURLRef {
   // the data for some search terms. Most of the time ReplaceSearchTerms should
   // be called.
   std::string ReplaceSearchTermsUsingTermsData(
+      Profile* profile,

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

This too may be invoked from any thread, which implies it should not take a
Profile.

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

I am not sure how to interpret this.

Is the concern that if this takes a Profile* (which implies that it could modify
Profile), then multiple threads could call it without locking, with a potential
for data corruption? This could be fixed by guarding uses of the Profile* with a
lock (in instant_field_trial.cc), or even better, just making this a "const
Profile*" (I'll need to make some upstream changes to make
Profile::IsOffTheRecord() and Profile::GetPrefs() const, which they technically
are, but just aren't marked so).

Or, is the concern that the Profile could change from underneath a thread while
another thread is using it? This would seem to cause a lot more headaches in the
rest of Chrome (i.e., not just in this code), so I don't think this is the
concern, right?

If you are saying that this absolutely should not take a Profile at all, then
could you propose an alternative of how to achieve my goal (of passing the
necessary Profile information to the Instant field trial code)?

       const TemplateURL& host,
       const string16& terms,
       int accepted_suggestion,
@@ -162,6 +165,7 @@ class TemplateURLRef {
     GOOGLE_RLZ,
     GOOGLE_SEARCH_FIELDTRIAL_GROUP,
     GOOGLE_UNESCAPED_SEARCH_TERMS,
+    INSTANT_FIELD_TRIAL_GROUP,
     LANGUAGE,
     SEARCH_TERMS,
   };