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..6892ede6c943435d831bf4f3b09cd63f3b41bcb6 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.
 //
@@ -343,19 +343,16 @@ const char* GetChromeFrameUserAgent() {
 
 std::string AddChromeFrameToUserAgentValue(const std::string& value) {
   if (value.empty()) {
-    DLOG(WARNING) << "empty user agent value";
-    return "";
+    return value;
   }
 
-  DCHECK_EQ(false, StartsWithASCII(value, "User-Agent:", true));
-
   if (value.find(kChromeFrameUserAgent) != std::string::npos) {
     // Our user agent has already been added.
     return value;
   }
 
   std::string ret(value);
-  std::string::size_type insert_position = ret.find(')');
+  size_t insert_position = ret.find(')');
   if (insert_position != std::string::npos) {
     if (insert_position > 1 && isalnum(ret[insert_position - 1]))
       ret.insert(insert_position++, ";");
@@ -369,6 +366,38 @@ std::string AddChromeFrameToUserAgentValue(const std::string& value) {
   return ret;
 }
 
+std::string RemoveChromeFrameFromUserAgentValue(const std::string& value) {
+  size_t cf_start = value.find(kChromeFrameUserAgent);
+  if (cf_start == std::string::npos) {
+    // The user agent is not present.
+    return value;
+  }
+
+  size_t offset = 0;
+  // If we prepended a '; ' or a ' ' then remove that in the output.
+  if (cf_start > 1 && value[cf_start - 1] == ' ')
+    ++offset;
+  if (cf_start > 3 &&
+      value[cf_start - 2] == ';' &&
+      isalnum(value[cf_start - 3])) {
+    ++offset;
+  }
+
+  std::string ret(value, 0, std::max(cf_start - offset, 0U));
+  cf_start += strlen(kChromeFrameUserAgent);
+  while (cf_start < value.length() &&
+         ((value[cf_start] >= '0' && value[cf_start] <= '9') ||
+          value[cf_start] == '.' ||
+          value[cf_start] == '/')) {
+    ++cf_start;
+  }
+
+  if (cf_start < value.length())
+    ret.append(value, cf_start, std::string::npos);
+
+  return ret;
+}
+
 std::string GetDefaultUserAgentHeaderWithCFTag() {
   std::string ua(GetDefaultUserAgent());
   return "User-Agent: " + AddChromeFrameToUserAgentValue(ua);