[PPAPI] Added VarResource_Dev class.

ppapi/cpp/file_system.cc

Index: ppapi/cpp/file_system.cc
diff --git a/ppapi/cpp/file_system.cc b/ppapi/cpp/file_system.cc
index f993fdaa892459a036ff94192b5fd5460373ba08..a2edef45cad210db73009700023e53b62903c8fd 100644
--- a/ppapi/cpp/file_system.cc
+++ b/ppapi/cpp/file_system.cc
@@ -9,6 +9,7 @@
 #include "ppapi/cpp/completion_callback.h"
 #include "ppapi/cpp/file_ref.h"
 #include "ppapi/cpp/instance_handle.h"
+#include "ppapi/cpp/logging.h"
 #include "ppapi/cpp/module.h"
 #include "ppapi/cpp/module_impl.h"
 
@@ -28,6 +29,15 @@ FileSystem::FileSystem() {
 FileSystem::FileSystem(const FileSystem& other) : Resource(other) {
 }
 
+FileSystem::FileSystem(Resource resource) : Resource(resource) {
+  if (!ResourceIsFileSystem(resource)) {
+    PP_NOTREACHED();
+
+    // On release builds, set this to null.
+    Clear();
+  }
+}
+
 FileSystem::FileSystem(PassRef, PP_Resource resource)
     : Resource(PASS_REF, resource) {
 }
@@ -48,4 +58,12 @@ int32_t FileSystem::Open(int64_t expected_size,
       pp_resource(), expected_size, cc.pp_completion_callback());
 }
 
+// static
+bool FileSystem::ResourceIsFileSystem(const Resource& resource) {
+  if (!has_interface<PPB_FileSystem_1_0>())
+    return false;
+  return get_interface<PPB_FileSystem_1_0>()->IsFileSystem(
+      resource.pp_resource());
+}
+
 }  // namespace pp