net: add IsMethodSafe() method to HttpUtil

net/http/http_util.h

Index: net/http/http_util.h
diff --git a/net/http/http_util.h b/net/http/http_util.h
index cb3de359c1d58f101d0f08efdae5b5fd1721dbd9..5903238288a4ca1149414e3c11356fb59f9224f2 100644
--- a/net/http/http_util.h
+++ b/net/http/http_util.h
@@ -75,6 +75,9 @@ class NET_EXPORT HttpUtil {
                                     base::Time now,
                                     base::TimeDelta* retry_after);
 
+  // True if the request method is "safe" (per section 4.2.1 of RFC 7231).
+  static bool IsMethodSafe(const std::string& method);
+
   // Returns true if it is safe to allow users and scripts to specify the header
   // named |name|.
   static bool IsSafeHeader(const std::string& name);