Add utility method for WebString to base::FilePath conversion

third_party/WebKit/Source/platform/exported/FilePathConversion.cpp

+// Copyright 2016 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 "public/platform/FilePathConversion.h"
+
+#include "base/files/file_path.h"
+#include "public/platform/WebString.h"
+#include "wtf/text/StringUTF8Adaptor.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+base::FilePath WebStringToFilePath(const WebString& webString)
+{
+    if (webString.isEmpty())
+        return base::FilePath();
+
+    String str = webString;
+    if (!str.is8Bit()) {
+        return base::FilePath::FromUTF16Unsafe(
+            base::StringPiece16(str.characters16(), str.length()));
+    }
+
+#if OS(POSIX)
+    StringUTF8Adaptor utf8(str);
+    return base::FilePath::FromUTF8Unsafe(utf8.asStringPiece());
+#else
+    const LChar* data8 = str.characters8();
+    return base::FilePath::FromUTF16Unsafe(
+        base::string16(data8, data8 + str.length()));
+#endif
+}
+
+} // namespace blink