Use the WebKit default fonts when specifying generic font families.

webkit/plugins/ppapi/mock_plugin_delegate.cc

Index: webkit/plugins/ppapi/mock_plugin_delegate.cc
===================================================================
--- webkit/plugins/ppapi/mock_plugin_delegate.cc	(revision 86722)
+++ webkit/plugins/ppapi/mock_plugin_delegate.cc	(working copy)
@@ -6,6 +6,7 @@
 
 #include "base/message_loop_proxy.h"
 #include "ppapi/c/pp_errors.h"
+#include "ppapi/shared_impl/ppapi_preferences.h"
 
 namespace webkit {
 namespace ppapi {
@@ -248,5 +249,9 @@
   return NULL;
 }
 
+::ppapi::Preferences MockPluginDelegate::GetPreferences() {
+  return ::ppapi::Preferences();
+}
+
 }  // namespace ppapi
 }  // namespace webkit