Introduce webkit_glue::Latin1OrUTF16ToUTF16

This function is helpful for converting WebStrings to string16s. See
https://codereview.chromium.org/15866003/ for more context about why we need
this function defined in base rather than in Blink.

R=darin

Review URL: https://chromiumcodereview.appspot.com/15720004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202644 0039d316-1c4b-4281-b951-d872f2087c98

webkit/glue/latin1_string_conversions.cc

+// Copyright 2013 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 "webkit/glue/latin1_string_conversions.h"
+
+namespace webkit_glue {
+
+string16 Latin1OrUTF16ToUTF16(size_t length,
+                              const Latin1Char* latin1,
+                              const char16* utf16) {
+  if (!length)
+    return string16();
+  if (latin1)
+    return string16(latin1, latin1 + length);
+  return string16(utf16, utf16 + length);
+}
+
+}  // namespace webkit_glue

webkit/glue/latin1_string_conversions.h

+// Copyright 2013 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.
+
+#ifndef WEBKIT_GLUE_LATIN1_STRING_CONVERSIONS_H_
+#define WEBKIT_GLUE_LATIN1_STRING_CONVERSIONS_H_
+
+#include <string>
+
+#include "base/base_export.h"
+#include "base/string16.h"
+#include "webkit/glue/webkit_glue_export.h"
+
+namespace webkit_glue {
+
+// This definition of Latin1Char matches the definition of LChar in Blink. We
+// use unsigned char rather than char to make less tempting to mix and match
+// Latin-1 and UTF-8 characters..
+typedef unsigned char Latin1Char;
+
+// This somewhat odd function is designed to help us convert from Blink Strings
+// to string16. A Blink string is either backed by an array of Latin-1
+// characters or an array of UTF-16 characters. This function is called by
+// WebString::operator string16() to convert one or the other character array
+// to string16. This function is defined here rather than in WebString.h to
+// avoid binary bloat in all the callers of the conversion operator.
+WEBKIT_GLUE_EXPORT string16 Latin1OrUTF16ToUTF16(size_t length,
+                                                 const Latin1Char* latin1,
+                                                 const char16* utf16);
+
+}  // namespace webkit_glue
+
+#endif  // WEBKIT_GLUE_LATIN1_STRING_CONVERSIONS_H_

webkit/glue/webkit_glue.gypi

@@ -206,6 +206,8 @@
         'glue_serialize.h',
         'image_decoder.cc',
         'image_decoder.h',
+        'latin1_string_conversions.cc',
+        'latin1_string_conversions.h',
         'network_list_observer.h',
         'npruntime_util.cc',
         'npruntime_util.h',