Add a SetCanonicalCookie method for CookieMonster.

net/cookies/canonical_cookie.h

Index: net/cookies/canonical_cookie.h
diff --git a/net/cookies/canonical_cookie.h b/net/cookies/canonical_cookie.h
index 1d3b3ed5337debcdfef591bfa54837bef56fdbe4..78870ec5a1306b769a2f38fc59882e2f40b7024d 100644
--- a/net/cookies/canonical_cookie.h
+++ b/net/cookies/canonical_cookie.h
@@ -47,8 +47,8 @@ class NET_EXPORT CanonicalCookie {
   // Supports the default copy constructor.
 
   // Creates a new |CanonicalCookie| from the |cookie_line| and the
-  // |creation_time|. Canonicalizes and validates inputs. May return NULL if
-  // an attribute value is invalid.
+  // |creation_time|.  Canonicalizes and validates inputs. May return NULL if
+  // an attribute value is invalid.  |creation_time| may not be null.
   static std::unique_ptr<CanonicalCookie> Create(
       const GURL& url,
       const std::string& cookie_line,
@@ -159,6 +159,11 @@ class NET_EXPORT CanonicalCookie {
   // greater than the last access time.
   bool IsCanonical() const;
 
+  // Sets the creation date of the cookie to the specified value.  It
+  // is only valid to call this method if the existing creation date
+  // is null.
+  void SetCreationDate(base::Time new_creation_date);
+
  private:
   FRIEND_TEST_ALL_PREFIXES(CanonicalCookieTest, TestPrefixHistograms);