Add a sampling profiler and a script to generate profiles for use with Gecko tooling.

ports/libsimpleservo/api/src/lib.rs

@@ -519,7 +519,8 @@ impl ServoGlue {
                 EmbedderMsg::SetFullscreenState(..) |
                 EmbedderMsg::ShowIME(..) |
                 EmbedderMsg::HideIME |
-                EmbedderMsg::Panic(..) => {},
+                EmbedderMsg::Panic(..) |
+                EmbedderMsg::ReportProfile(..) => {},
             }
         }
         Ok(())