PPAPI: Add Quota info to PPB_FileSystem::Open doc

ppapi/cpp/file_system.h

Index: ppapi/cpp/file_system.h
diff --git a/ppapi/cpp/file_system.h b/ppapi/cpp/file_system.h
index 8aea7a555c5fb3ae6a1981df7293738211de609a..ab95a334cf2fa5b0a89f81c0bffab6958f84241b 100644
--- a/ppapi/cpp/file_system.h
+++ b/ppapi/cpp/file_system.h
@@ -40,7 +40,13 @@ class FileSystem : public Resource {
   /// 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().
   ///