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

chrome/browser/chromeos/gdata/gdata_util.h

Index: chrome/browser/chromeos/gdata/gdata_util.h
diff --git a/chrome/browser/chromeos/gdata/gdata_util.h b/chrome/browser/chromeos/gdata/gdata_util.h
index 41555bc6199e161ccc44986a2b156d2483999f07..04e5e6d6fae9f7510de6a9c4dc6fc6d78486a2bd 100644
--- a/chrome/browser/chromeos/gdata/gdata_util.h
+++ b/chrome/browser/chromeos/gdata/gdata_util.h
@@ -110,6 +110,22 @@ 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.
+//
+// Must be called from UI thread.
+void PrepareWritableFileAndRun(Profile* profile,
+                               const FilePath& path,
+                               const OpenFileCallback& callback);
+
 }  // namespace util
 }  // namespace gdata