Update toolbar on format

This change fixes the following bug:

  1. Start with plain text "foo bar" in the editor
  2. Highlight "bar" (NB: it's important to select text that's not at
     the start)
  3. Hit Ctrl+B to apply bold formatting
  4. Notice that the bold button in the toolbar doesn't receive the
     `ql-active` class, when it should

This appears to happen because the listener on `SCROLL_OPTIMIZE` gets an
incorrect range.

Instead of listening on optimize, we listen for all `EDITOR_CHANGE`
events, which _do_ get the correct range.

modules/toolbar.js

@@ -33,12 +33,7 @@ class Toolbar extends Module {
         this.attach(input);
       },
     );
-    this.quill.on(Quill.events.EDITOR_CHANGE, (type, range) => {
-      if (type === Quill.events.SELECTION_CHANGE) {
-        this.update(range);
-      }
-    });
-    this.quill.on(Quill.events.SCROLL_OPTIMIZE, () => {
+    this.quill.on(Quill.events.EDITOR_CHANGE, () => {
       const [range] = this.quill.selection.getRange(); // quill.getSelection triggers update
       this.update(range);
     });

test/unit/modules/toolbar.js

@@ -181,5 +181,15 @@ describe('Toolbar', function() {
       expect(centerButton.classList.contains('ql-active')).toBe(false);
       expect(leftButton.classList.contains('ql-active')).toBe(false);
     });
+
+    it('update on format', function() {
+      const boldButton = this.container.parentNode.querySelector(
+        'button.ql-bold',
+      );
+      this.quill.setSelection(1, 2);
+      expect(boldButton.classList.contains('ql-active')).toBe(false);
+      this.quill.format('bold', true, 'user');
+      expect(boldButton.classList.contains('ql-active')).toBe(true);
+    });
   });
 });