Make Isolated file system writable only if it is configured so

webkit/fileapi/test_mount_point_provider.cc

Index: webkit/fileapi/test_mount_point_provider.cc
diff --git a/webkit/fileapi/test_mount_point_provider.cc b/webkit/fileapi/test_mount_point_provider.cc
index 20e716d0b82eefc50029087c50c78f7b3c3fb308..ce8dfc80f0a2c58e7ac7dc9d831af65ea75f2e37 100644
--- a/webkit/fileapi/test_mount_point_provider.cc
+++ b/webkit/fileapi/test_mount_point_provider.cc
@@ -16,6 +16,7 @@
 #include "webkit/fileapi/file_system_util.h"
 #include "webkit/fileapi/local_file_util.h"
 #include "webkit/fileapi/native_file_util.h"
+#include "webkit/fileapi/sandbox_file_stream_writer.h"
 #include "webkit/quota/quota_manager.h"
 
 namespace fileapi {
@@ -156,9 +157,7 @@ fileapi::FileStreamWriter* TestMountPointProvider::CreateFileStreamWriter(
     const GURL& url,
     int64 offset,
     FileSystemContext* context) const {
-  // TODO(kinaba,kinuko): return SandboxFileWriter when it is implemented.
-  NOTIMPLEMENTED();
-  return NULL;
+  return new SandboxFileStreamWriter(context, url, offset);
 }
 
 FileSystemQuotaUtil* TestMountPointProvider::GetQuotaUtil() {