Add confidence to AutocompleteMatch.

chrome/browser/autocomplete/autocomplete_match.h

Index: chrome/browser/autocomplete/autocomplete_match.h
diff --git a/chrome/browser/autocomplete/autocomplete_match.h b/chrome/browser/autocomplete/autocomplete_match.h
index fbf835534793cbaa0441c76e040ec1962f4dfbec..6fbb78018639f92131a20143b59706684aeb4b66 100644
--- a/chrome/browser/autocomplete/autocomplete_match.h
+++ b/chrome/browser/autocomplete/autocomplete_match.h
@@ -85,6 +85,7 @@ struct AutocompleteMatch {
   AutocompleteMatch();
   AutocompleteMatch(AutocompleteProvider* provider,
                     int relevance,
+                    float confidence,
                     bool deletable,
                     Type type);
   ~AutocompleteMatch();
@@ -139,6 +140,10 @@ struct AutocompleteMatch {
   // rather than being a fairly fixed value defined by the table above.
   int relevance;
 
+  // The confidence of the match. Calculated per provider and a measure in the
+  // range [0, 1].
+  float confidence;
+
   // True if the user should be able to delete this match.
   bool deletable;