Added HttpUtils::HasValidators and HttpResponse::HasValidators

net/http/http_util.cc

Index: net/http/http_util.cc
diff --git a/net/http/http_util.cc b/net/http/http_util.cc
index 6192c894145db1310e9668fbcfaebc89a260065f..31d15169515ff49170c45045a36b53f19cb51ce1 100644
--- a/net/http/http_util.cc
+++ b/net/http/http_util.cc
@@ -738,6 +738,9 @@ bool HttpUtil::HasStrongValidators(HttpVersion version,
                                    const std::string& etag_header,
                                    const std::string& last_modified_header,
                                    const std::string& date_header) {
+  if (!HasValidators(version, etag_header, last_modified_header))
+    return false;
+
   if (version < HttpVersion(1, 1))

[gavinp, 2016/02/26 15:32:59]

Nit: I think this is redundant now.

[jamartin, 2016/02/29 14:40:01]

No, it isn't. A message with LastModified, ETag and v1.0 would be wrongly
considered as HasStrongValidators = True. Granted this should not occur since
ETag were only introduced in HTTP v1.1 but I better be safe than sorry.

[gavinp, 2016/02/29 14:44:01]

Good point. I agree. Thanks.

     return false;
 
@@ -761,9 +764,27 @@ bool HttpUtil::HasStrongValidators(HttpVersion version,
   if (!base::Time::FromString(date_header.c_str(), &date))
     return false;
 
+  // Last-Modified is implicitly weak unless it is at least 60 seconds before
+  // the Date value.
   return ((date - last_modified).InSeconds() >= 60);
 }
 
+bool HttpUtil::HasValidators(HttpVersion version,
+                             const std::string& etag_header,
+                             const std::string& last_modified_header) {
+  if (version < HttpVersion(1, 0))
+    return false;
+
+  base::Time last_modified;
+  if (base::Time::FromString(last_modified_header.c_str(), &last_modified))
+    return true;
+
+  // It is OK to consider an empty string in etag_header to be a missing header
+  // since valid ETags are always quoted-strings (see RFC 2616 3.11) and thus
+  // empty ETags aren't empty strings (i.e., "\"\"").

[gavinp, 2016/02/26 15:32:59]

Nit: how about (i.e. an empty ETag might be "\"\"") so it's totally
unambiguously clear you're not giving an example of a nonempty ETag?

[jamartin, 2016/02/29 14:40:01]

Done.

+  return version >= HttpVersion(1, 1) && !etag_header.empty();
+}
+
 // Functions for histogram initialization.  The code 0 is put in the map to
 // track status codes that are invalid.
 // TODO(gavinp): Greatly prune the collected codes once we learn which