Omnibox: Create Bundled Field Trial; Convert SearchHistory trial to it

chrome/browser/autocomplete/search_provider.h

Index: chrome/browser/autocomplete/search_provider.h
diff --git a/chrome/browser/autocomplete/search_provider.h b/chrome/browser/autocomplete/search_provider.h
index 3f9b080a20fc503842a26d42afc77d31239dbd33..f04c7011804060d687bfba94b331efa44fb8b584 100644
--- a/chrome/browser/autocomplete/search_provider.h
+++ b/chrome/browser/autocomplete/search_provider.h
@@ -436,10 +436,13 @@ class SearchProvider : public AutocompleteProvider,
   // |time| is the time at which this query was last seen.  |is_keyword|
   // indicates whether the results correspond to the keyword provider or default
   // provider. |prevent_inline_autocomplete| is true if we should not inline
-  // autocomplete this query.
+  // autocomplete this query.  |prevent_search_history_inlining| is true
+  // if we would normally inline autocomplete this query but want to shift
+  // the relevance curve slightly downward.

[Peter Kasting, 2013/08/01 22:44:48]

Nit: You might want a clearer explanation of these last two params (and maybe
even different names for them).  Basically, you'd want to explain that we have
two scoring curves, and why; then if |prevent_inline_autocomplete| is true, note
that we force all searches to use the second curve, and the last arg is ignored,
while if |prevent_inline_autocomplete| is false but
|prevent_search_history_inlining| is true, we allow two scoring curves to be
used, but lower the top value of the first curve.

Writing all that out makes me think that maybe this whole "2-curve, 2-param"
combination is more complex than it really should be.  After all, if it's hard
to explain...

[Mark P, 2013/08/02 00:44:36]

With judicious renaming, I think I managed to rewrite the comment in a much
clearer way.  I agree the old way with two "prevent" variables was ugly.

   int CalculateRelevanceForHistory(const base::Time& time,
                                    bool is_keyword,
-                                   bool prevent_inline_autocomplete) const;
+                                   bool prevent_inline_autocomplete,
+                                   bool prevent_search_history_inlining) const;
 
   // Creates an AutocompleteMatch for "Search <engine> for |query_string|" with
   // the supplied relevance.  Adds this match to |map|; if such a match already
@@ -531,9 +534,6 @@ class SearchProvider : public AutocompleteProvider,
   // they will not be inlined.
   bool prevent_search_history_inlining_;
 
-  // If true, no search history query suggestions will be offered.
-  bool disable_search_history_;
-
   DISALLOW_COPY_AND_ASSIGN(SearchProvider);
 };