When a font family pref changes to the empty string, pass it to WebKit.

chrome/common/pref_names_util.cc

Index: chrome/common/pref_names_util.cc
diff --git a/chrome/common/pref_names_util.cc b/chrome/common/pref_names_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1b1e4dd4d5b56a56f569f6be40af63554278d0f5
--- /dev/null
+++ b/chrome/common/pref_names_util.cc
@@ -0,0 +1,30 @@
+// 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.
+
+#include "chrome/common/pref_names_util.h"
+
+#include "base/string_util.h"
+
+namespace pref_names_util {
+
+const char kWebKitFontPrefPrefix[] = "webkit.webprefs.fonts.";
+
+bool ParseFontNamePrefPath(const std::string& pref_path,
+                           std::string* generic_family,
+                           std::string* script) {
+  if (!StartsWithASCII(pref_path, kWebKitFontPrefPrefix, true))
+    return false;
+
+  size_t start = strlen(kWebKitFontPrefPrefix);
+  size_t pos = pref_path.find('.', start);
+  if (pos == std::string::npos || pos + 1 == pref_path.length())
+    return false;
+  if (generic_family)
+    *generic_family = pref_path.substr(start, pos - start);
+  if (script)
+    *script = pref_path.substr(pos + 1);
+  return true;
+}
+
+}  // namespace pref_names_util