[PPAPI] Added VarResource_Dev class.

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 9baa78e31bf8d21c843a59eeaa2aa5b7c2cd550c..96e88c1a324b683b6857d9a2fb4d05c4d2c31789 100644
--- a/ppapi/cpp/file_system.h
+++ b/ppapi/cpp/file_system.h
@@ -33,6 +33,11 @@ class FileSystem : public Resource {
   /// @param[in] other A reference to a <code>FileSystem</code>.
   FileSystem(const FileSystem& other);
 
+  /// Constructs a <code>FileSystem</code> from a <code>Resource</code>.
+  ///
+  /// @param[in] resource A <code>Resource</code> containing a file system.
+  explicit FileSystem(const Resource& resource);
+
   /// A constructor used when you have received a PP_Resource as a return
   /// value that has already been reference counted.
   ///
@@ -63,6 +68,14 @@ class FileSystem : public Resource {
   ///
   /// @return An int32_t containing an error code from <code>pp_errors.h</code>.
   int32_t Open(int64_t expected_size, const CompletionCallback& cc);
+
+  /// Checks whether a <code>Resource</code> is a file system, to test whether
+  /// it is appropriate for use with the <code>FileSystem</code> constructor.
+  ///
+  /// @param[in] resource A <code>Resource</code> to test.
+  ///
+  /// @return True if <code>resource</code> is a file system.
+  static bool IsFileSystem(const Resource& resource);
 };
 
 }  // namespace pp