gdata: Convert FindEntryByResourceIdSync() to asynchronous.

chrome/browser/chromeos/gdata/gdata_files.h

Index: chrome/browser/chromeos/gdata/gdata_files.h
diff --git a/chrome/browser/chromeos/gdata/gdata_files.h b/chrome/browser/chromeos/gdata/gdata_files.h
index bc6f7f7897a57e62c21cf6bacbd3e076c84dd7c2..6f970adf1bf82cded3645cf6d2e3ad088ae048cb 100644
--- a/chrome/browser/chromeos/gdata/gdata_files.h
+++ b/chrome/browser/chromeos/gdata/gdata_files.h
@@ -17,7 +17,6 @@
 #include "base/memory/weak_ptr.h"
 #include "base/platform_file.h"
 #include "base/synchronization/lock.h"
-#include "chrome/browser/chromeos/gdata/find_entry_callback.h"
 #include "chrome/browser/chromeos/gdata/gdata_params.h"
 #include "chrome/browser/chromeos/gdata/gdata_parser.h"
 #include "chrome/browser/chromeos/gdata/gdata_uploader.h"
@@ -26,6 +25,7 @@
 
 namespace gdata {
 
+class GDataEntry;
 class GDataFile;
 class GDataDirectory;
 class GDataRootDirectory;
@@ -64,6 +64,11 @@ const FilePath::CharType kGDataRootDirectory[] = FILE_PATH_LITERAL("drive");
 // https://developers.google.com/google-apps/documents-list/
 const char kGDataRootDirectoryResourceId[] = "folder:root";
 
+// Used to get result of file search.
+// If |error| is not PLATFORM_FILE_OK, |entry| is set to NULL.
+typedef base::Callback<void(base::PlatformFileError error, GDataEntry* entry)>
+    FindEntryCallback;
+
 // Base class for representing files and directories in gdata virtual file
 // system.
 class GDataEntry {