pp::FileSystem: add copy constrctor

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 de14c369f94d794b8ddfda86c2bfd069c5ca9ba8..f993fdaa892459a036ff94192b5fd5460373ba08 100644
--- a/ppapi/cpp/file_system.cc
+++ b/ppapi/cpp/file_system.cc
@@ -25,6 +25,9 @@ template <> const char* interface_name<PPB_FileSystem_1_0>() {
 FileSystem::FileSystem() {
 }
 
+FileSystem::FileSystem(const FileSystem& other) : Resource(other) {
+}
+
 FileSystem::FileSystem(PassRef, PP_Resource resource)
     : Resource(PASS_REF, resource) {
 }