Add a setting to CF to remove 'chromeframe' from the UserAgent on a per-pattern basis.

chrome_frame/html_utils.cc

Index: chrome_frame/html_utils.cc
diff --git a/chrome_frame/html_utils.cc b/chrome_frame/html_utils.cc
index 3121a756fa786fa0556201e1625e6171e5bde094..e0c645ed48421f8dc18dc81f90b55d9af6a84b4d 100644
--- a/chrome_frame/html_utils.cc
+++ b/chrome_frame/html_utils.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 //
@@ -369,6 +369,40 @@ std::string AddChromeFrameToUserAgentValue(const std::string& value) {
   return ret;
 }
 
+
+std::string RemoveChromeFrameFromUserAgentValue(const std::string& value) {
+  if (value.empty()) {
+    DLOG(WARNING) << "empty user agent value";
+    return "";
+  }
+
+  DCHECK_EQ(false, StartsWithASCII(value, "User-Agent:", true));

[slightlyoff1, 2012/03/20 15:31:56]

What's the rationale for this check? Is it that we should only be dealing with
the value, not the header name? If so, can we get a comment here quickly
outlining the thinking/

[robertshield, 2012/03/26 02:43:33]

I was following the tradition established in AddChromeFrameToUserAgentValue of
ensuring that this function is only called on an actual User-Agent header
string. This isn't documented in the header comments though and seems generally
unnecessary, so I'm removing it.

+
+  std::string::size_type cf_start = value.find(kChromeFrameUserAgent);

[grt (UTC plus 2), 2012/03/20 17:27:45]

Chromium style says to use size_t instead of size_type

[robertshield, 2012/03/26 02:43:33]

Fixed here and above.

+  if (cf_start == std::string::npos) {
+    // The user agent is not present.
+    return value;
+  }
+
+  int offset = 0;
+  // If we prepended a '; ' or a ' ' then remove that in the output.
+  if (cf_start > 1 && value[cf_start - 1] == ' ') ++offset;

[grt (UTC plus 2), 2012/03/20 17:27:45]

nit: i find this single-line stuff foreign enough that it reduces readability. 
please wrap if you don't mind.

[robertshield, 2012/03/26 02:43:33]

Done.

+  if (cf_start > 2 && value[cf_start - 2] == ';') ++offset;
+
+  std::string ret(value, 0, cf_start - offset);

[slightlyoff1, 2012/03/20 15:31:56]

can we get a check to make sure that cf_start - offset >= 0?

[robertshield, 2012/03/26 02:43:33]

Sure, added. Note that since cf_start is a positive integer, it can be proven
that the three lines above guarantee that cf_cstart - offset >= 0. Check added
for clarity anyway.

+  cf_start += strlen(kChromeFrameUserAgent);
+  while (cf_start < value.length() &&
+         (value[cf_start] == '/' ||

[grt (UTC plus 2), 2012/03/20 17:27:45]

nit: order these clauses from most-likely-to-match to least-likely-to-match

[robertshield, 2012/03/26 02:43:33]

Indeed!

+          value[cf_start] == '.' ||
+          (value[cf_start] >= '0' && value[cf_start] <= '9'))) {
+    ++cf_start;
+  }
+  if (cf_start < value.length())
+    ret += value.substr(cf_start);
+
+  return ret;
+}
+
 std::string GetDefaultUserAgentHeaderWithCFTag() {
   std::string ua(GetDefaultUserAgent());
   return "User-Agent: " + AddChromeFrameToUserAgentValue(ua);