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

chrome/browser/search_engines/search_terms_data.h

Index: chrome/browser/search_engines/search_terms_data.h
diff --git a/chrome/browser/search_engines/search_terms_data.h b/chrome/browser/search_engines/search_terms_data.h
index a695a113c7eca0c3c50913ef03895142f98e1622..887c4d8e91772d20cfc79c2fc216ed4761be3f14 100644
--- a/chrome/browser/search_engines/search_terms_data.h
+++ b/chrome/browser/search_engines/search_terms_data.h
@@ -11,6 +11,8 @@
 #include "base/basictypes.h"
 #include "base/string16.h"
 
+class Profile;
+
 // All data needed by TemplateURLRef::ReplaceSearchTerms which typically may
 // only be accessed on the UI thread.
 class SearchTermsData {
@@ -32,6 +34,11 @@ class SearchTermsData {
   virtual string16 GetRlzParameterValue() const = 0;
 #endif
 
+  // Returns a string indicating the Instant field trial group, suitable for
+  // adding as a query string param to suggest/search URLs, or an empty string
+  // if the field trial is not active.

[Peter Kasting, 2011/08/11 18:04:34]

Nit: Might want to add "Checking this requires accessing the Profile, which
means this can only ever be non-empty for UIThreadSearchTermsData."

[sreeram, 2011/08/11 18:22:19]

Done.

+  virtual std::string InstantFieldTrialUrlParam() const;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(SearchTermsData);
 };
@@ -47,14 +54,21 @@ class UIThreadSearchTermsData : public SearchTermsData {
 #if defined(OS_WIN) && defined(GOOGLE_CHROME_BUILD)
   virtual string16 GetRlzParameterValue() const;
 #endif
+  virtual std::string InstantFieldTrialUrlParam() const;

[Peter Kasting, 2011/08/11 18:04:34]

Nit: Add comment: "// This returns the empty string unless set_profile() has
been called."

[sreeram, 2011/08/11 18:22:19]

Done.

 
   // Used by tests to set the value for the Google base url. This takes
   // ownership of the given std::string.
   static void SetGoogleBaseURL(std::string* google_base_url);
 
+  // Optionally, set the profile to be used to look up params for the Instant

[Peter Kasting, 2011/08/11 18:04:34]

Nit: I'd move this below the constructor and make it:

  // Callers who need an accurate answer from InstantFieldTrialUrlParam() must
  // set the profile here before calling that.
  void set_profile(Profile* profile) { profile_ = profile; }

Note that because this doesn't actually access the profile, we can get away with
not checking that we're on the UI thread -- we'll do that check when we actually
try to read it.

+  // field trial.
+  void SetProfile(Profile* profile);
+
  private:
   static std::string* google_base_url_;
 

[Peter Kasting, 2011/08/11 18:04:34]

Nit: Unnecessary newline

[sreeram, 2011/08/11 18:22:19]

Done.

+  Profile* profile_;
+
   DISALLOW_COPY_AND_ASSIGN(UIThreadSearchTermsData);
 };