PPAPI: Implement operator= for FileChooser_Trusted.

ppapi/cpp/trusted/file_chooser_trusted.h

Index: ppapi/cpp/trusted/file_chooser_trusted.h
diff --git a/ppapi/cpp/trusted/file_chooser_trusted.h b/ppapi/cpp/trusted/file_chooser_trusted.h
index a0227ef030812bad69be86e82401712506feed67..352ac12fb28a7e861f7608ebd68bbe505a4c6d76 100644
--- a/ppapi/cpp/trusted/file_chooser_trusted.h
+++ b/ppapi/cpp/trusted/file_chooser_trusted.h
@@ -24,13 +24,15 @@ class FileChooser_Trusted : public FileChooser_Dev {
 
   FileChooser_Trusted(const FileChooser_Trusted& other);
 
+  FileChooser_Trusted& operator=(const FileChooser_Trusted& other);
+
   // Overrides of method in superclass. This shows without requiring a user
   // gesture (and can also show save dialogs).
   virtual int32_t Show(const CompletionCallback& cc);
 
  private:
-  const bool save_as_;
-  const std::string suggested_file_name_;
+  bool save_as_;
+  std::string suggested_file_name_;
 };
 
 }  // namespace pp