[Enhancement] Add IE, Opera, Safari support for canvas.toBlob()

This is currently being used for exporting plots to PNG/JPG.

platform/features/plot/src/services/ExportImageService.js

@@ -101,6 +101,30 @@ define(
             return defer.promise;
         }
 
+        /**
+         * canvas.toBlob() not supported in IE < 10, Opera, and Safari. This polyfill
+         * implements the method in browsers that would not otherwise support it.
+         * https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toBlob
+         */
+        function polyfillToBlob() {
+            if (!HTMLCanvasElement.prototype.toBlob) {
+                Object.defineProperty(HTMLCanvasElement.prototype, "toBlob", {
+                    value: function (callback, type, quality) {
+
+                        var binStr = atob(this.toDataURL(type, quality).split(',')[1]),
+                            len = binStr.length,
+                            arr = new Uint8Array(len);
+
+                        for (var i = 0; i < len; i++) {
+                            arr[i] = binStr.charCodeAt(i);
+                        }
+
+                        callback(new Blob([arr], {type: type || "image/png"}));
+                    }
+                });
+            }
+        }
+
         ExportImageService.prototype.exportPDF = function (element, filename) {
             return renderElement(element, "jpeg").then(function (img) {
                 var pdf = new self.jsPDF("l", "px", [element.offsetHeight, element.offsetWidth]);
@@ -121,6 +145,8 @@ define(
             });
         };
 
+        polyfillToBlob();
+
         return ExportImageService;
     }
 );