Smoke test for tracing infrastructure in PyAuto

chrome/test/functional/tracing/timeline_model.js

+function invokeJsMethodFromPython(targetObject, methodName, args) {
+  var sendToPython = function(obj) {

[nduca, 2012/07/18 05:51:35]

How about this being tracing_test_shim.js -- and fusing the javascript code that
this does with the javascript code for getting a recording?

And have it define a TimelineModelShim object that is the shim between the
python model and the real model.

Then, define methods on that shim object that are methods you need for providing
certain data out to python.

[nduca, 2012/07/18 05:51:35]

This is a private method, only to be called by the code below. So, use
_sendToPython to denote it, or put the entire code in

base.defineModule('timeline_model_proxy_support')
        .exporstTo('tracing', function() {
   .... this code
   return { InvokeOnTimelineModel: InvokeOnTimelineModel };
});

That way you get module-local vars and a clearly defined export.

+    // We use sendJSON here because domAutomationController's send() chokes
+    // on large amounts of data. Inside of send() it converts the arg to
+    // JSON and invokes sendJSON. The JSON conversion is what fails. This

[nduca, 2012/07/18 05:51:35]

Why does the json conversion fail?

+    // way works around the bad code, but necessitates a double JSON
+    // conversion as the recieving python converts from JSON before passing
+    // it back to the pyauto test.
+    window.domAutomationController.sendJSON(
+      JSON.stringify(

[nduca, 2012/07/18 05:51:35]

I'm so confused. This makes no sense. Also, does sendJSON convert to json
internally?! So you're json-ing three times?!

+        JSON.stringify(obj)
+      )
+    );
+  };
+  try {

[nduca, 2012/07/18 05:51:35]

Why are you sourcing this file every time? You could just make this be a
function, e.g. InvokeOnTimelineModel, and load it at test start?

+    sendToPython({

[nduca, 2012/07/18 05:51:35]

Can't you break this up into individual lines instead of crazy method calls
inside method calls? Temp vars for the win, bro!

Also, why is sendToPython inside your exception handler?

+      success: true,
+      data: targetObject[methodName].apply(targetObject, JSON.parse(args))
+    });
+  } catch( e ) {
+    var ret = {
+      success: false,
+      message: 'Unspecified error'
+    };
+    if( typeof(e) == 'string' || e instanceof String ) {
+      ret.message = e;
+    } else {
+      if( e.stack != undefined ) ret.stack = e.stack;
+      if( e.message != undefined ) ret.message = e.message;
+    }
+    // First we'll try sending with the exception embedded, and if that
+    // doesn't work, try sending without the exception.

[nduca, 2012/07/18 05:51:35]

What? Why?

+    try {
+      sendToPython(ret);
+    } catch(e2) {
+      ret.exception = undefined;
+      sendToPython(ret);
+    }
+    throw e;
+  }
+}