gdata: Fix "save as pdf" to work on Google Drive.

chrome/browser/chromeos/gdata/gdata_util.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_GDATA_GDATA_UTIL_H_
 #define CHROME_BROWSER_CHROMEOS_GDATA_GDATA_UTIL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 92 matching lines @@
 base::PlatformFileError GDataFileErrorToPlatformError(GDataFileError error);
 
 // Parses an RFC 3339 date/time into a base::Time, returning true on success.
 // The time string must be in the format "yyyy-mm-ddThh:mm:ss.dddTZ" (TZ is
 // either '+hh:mm', '-hh:mm', 'Z' (representing UTC), or an empty string).
 bool GetTimeFromString(const base::StringPiece& raw_value, base::Time* time);
 
 // Formats a base::Time as an RFC 3339 date/time (in UTC).
 std::string FormatTimeAsString(const base::Time& time);
 
+// Callback type for PrepareWritableFilePathAndRun.
+typedef base::Callback<void (GDataFileError, const FilePath& path)>
+   OpenFileCallback;
+
+// Invokes |callback| on blocking thread pool, after converting virtual |path|
+// string like "/special/drive/foo.txt" to the concrete local cache file path.
+// After |callback| returns, the written content is synchronized to the server.
+//
+// If |path| is not a GData path, it is regarded as a local path and no path
+// conversion takes place.
+void PrepareWritableFileAndRun(Profile* profile,
+                               const FilePath& path,
+                               const OpenFileCallback& callback);
+
 }  // namespace util
 }  // namespace gdata
 
 #endif  // CHROME_BROWSER_CHROMEOS_GDATA_GDATA_UTIL_H_