Don't try to zoom flyouts and mutators (#2772)

* Don't try to zoom flyouts and mutators

Fixes #2752

Flyouts and mutator workspaces don't have enough info to handle
zooming correctly, so they were throwing errors if you pinched them.
This adds a check to quit a zoom early if in either of those. We
might want to revisit later if we should support zooming on them.

* Add TODO

core/workspace_svg.js

@@ -1690,6 +1690,12 @@ Blockly.WorkspaceSvg.prototype.setBrowserFocus = function() {
  *     amount values zoom in.
  */
 Blockly.WorkspaceSvg.prototype.zoom = function(x, y, amount) {
+  // TODO (#2782): Consider removing once pinch understands zoom configuration
+  // Mutators and flyouts don't support zooming, and pinch doesn't understand
+  // that.
+  if (this.isFlyout || this.isMutator) {
+    return;
+  }
   // Scale factor.
   var speed = this.options.zoomOptions.scaleSpeed;
   var scaleChange = Math.pow(speed, amount);