Clarify the documentation for url::{AddStandardScheme,IsStandard}.

url/gurl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef URL_GURL_H_
 #define URL_GURL_H_
 
 #include <iosfwd>
 #include <string>
 
@@ skipping 176 matching lines @@
   // It is an error to get the origin of an invalid URL. The result
   // will be the empty URL.
   GURL GetOrigin() const;
 
   // A helper function to return a GURL stripped from the elements that are not
   // supposed to be sent as HTTP referrer: username, password and ref fragment.
   // For invalid URLs or URLs that no valid referrers, an empty URL will be
   // returned.
   GURL GetAsReferrer() const;
 
-  // Returns true if the scheme for the current URL is a known "standard"
-  // scheme. Standard schemes have an authority and a path section. This
-  // includes file: and filesystem:, which some callers may want to filter out
-  // explicitly by calling SchemeIsFile[System].
+  // Returns true if the scheme for the current URL is a known "standard-format"
+  // scheme. A standard-format scheme adheres to what RFC 3986 calls "generic
+  // URI syntax" (https://tools.ietf.org/html/rfc3986#section-3). This includes
+  // file: and filesystem:, which some callers may want to filter out explicitly
+  // by calling SchemeIsFile[System].
   bool IsStandard() const;
 
   // Returns true if the given parameter (should be lower-case ASCII to match
   // the canonicalized scheme) is the scheme for this URL. This call is more
   // efficient than getting the scheme and comparing it because no copies or
   // object constructions are done.
   bool SchemeIs(const char* lower_ascii_scheme) const;
 
   // Returns true if the scheme is "http" or "https".
   bool SchemeIsHTTPOrHTTPS() const;
@@ skipping 206 matching lines @@
   // Used for nested schemes [currently only filesystem:].
   scoped_ptr<GURL> inner_url_;
 
   // TODO bug 684583: Add encoding for query params.
 };
 
 // Stream operator so GURL can be used in assertion statements.
 URL_EXPORT std::ostream& operator<<(std::ostream& out, const GURL& url);
 
 #endif  // URL_GURL_H_