PPAPI: Add Quota info to PPB_FileSystem::Open doc

ppapi/cpp/file_system.h

 // Copyright (c) 2011 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 PPAPI_CPP_FILE_SYSTEM_H_
 #define PPAPI_CPP_FILE_SYSTEM_H_
 
 #include "ppapi/c/pp_file_info.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_stdint.h"
@@ skipping 22 matching lines @@
   /// @param[in] instance The instance with which this resource will be
   /// associated.
   ///
   /// @param[in] type A file system type as defined by
   /// <code>PP_FileSystemType</code> enum.
   FileSystem(const InstanceHandle& instance, PP_FileSystemType type);
 
   /// Open() opens the file system. A file system must be opened before running
   /// any other operation on it.
   ///
-  /// @param[in] expected_size The expected size of the file system.
+  /// @param[in] expected_size The expected size of the file system. Note that
+  /// this does not request quota; to do that, you must either invoke
+  /// requestQuota from JavaScript:
+  /// http://www.html5rocks.com/en/tutorials/file/filesystem/#toc-requesting-quota
+  /// or set the unlimitedStorage permission for Chrome Web Store apps:
+  /// http://code.google.com/chrome/extensions/manifest.html#permissions
+  ///
   /// @param[in] cc A <code>PP_CompletionCallback</code> to be called upon
   /// completion of Open().
   ///
   /// @return An int32_t containing an error code from <code>pp_errors.h</code>.
   int32_t Open(int64_t expected_size, const CompletionCallback& cc);
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_FILE_SYSTEM_H_