fix find_output_cell for IPython >= 3.0

output mime-type keys moved from top-level to a `data` attribute.

Author: minrk

lib/matplotlib/backends/web_backend/nbagg_mpl.js

@@ -160,12 +160,15 @@ mpl.find_output_cell = function(html_output) {
     var ncells = cells.length;
     for (var i=0; i<ncells; i++) {
         var cell = cells[i];
-        if (cell.cell_type == 'code'){
+        if (cell.cell_type === 'code'){
             for (var j=0; j<cell.output_area.outputs.length; j++) {
                 var data = cell.output_area.outputs[j];
-                if (cell.output_area.outputs[j]['text/html'] == html_output) {
-                    var output = cell.output_area.outputs[j];
-                    return [cell, output, j];
+                if (data.data) {
+                    // IPython >= 3 moved mimebundle to data attribute of output
+                    data = data.data;
+                }
+                if (data['text/html'] == html_output) {
+                    return [cell, data, j];
                 }
             }
         }