Convert app_launch_index and page_index from int to StringOrdinal.

chrome/common/string_ordinal.h

Index: chrome/common/string_ordinal.h
diff --git a/chrome/common/string_ordinal.h b/chrome/common/string_ordinal.h
index abe0fe42da124d0408ace5ba171f51d568798a84..757f136700d926ddbfb2c03101921d60e0909755 100644
--- a/chrome/common/string_ordinal.h
+++ b/chrome/common/string_ordinal.h
@@ -29,6 +29,11 @@ class StringOrdinal {
   // Creates an invalid StringOrdinal.
   StringOrdinal();
 
+  // Creates a valid StringOrdinal, this is generally called to create the first
+  // element of StringOrdinal list (i.e. before we have any other values we can
+  // generate from).
+  static StringOrdinal CreateValidOrdinal();
+
   bool IsValid() const;
 
   // All remaining functions can only be called if IsValid() holds.
@@ -58,6 +63,13 @@ class StringOrdinal {
   // string will be valid.
   std::string ToString() const;
 
+  // A comparsion struct that can be use by STL containers that require sorting.
+  struct Comparsion {
+    bool operator() (const StringOrdinal& lhs, const StringOrdinal& rhs) const {
+      return lhs.LessThan(rhs);
+    }
+  };
+
   // Use of copy constructor and default assignment for this class is allowed.
 
  private: