Merge pull request scratchfoundation#5050 from paulkaplan/fix-recording-drag-firefox

Prevent default when dragging trim handles to prevent image drag

Author: paulkaplan

src/containers/audio-trimmer.jsx

@@ -42,11 +42,15 @@ class AudioTrimmer extends React.Component {
         this.containerSize = this.containerElement.getBoundingClientRect().width;
         this.trimStartDragRecognizer.start(e);
         this.initialTrim = this.props.trimStart;
+        e.stopPropagation();
+        e.preventDefault();
     }
     handleTrimEndMouseDown (e) {
         this.containerSize = this.containerElement.getBoundingClientRect().width;
         this.trimEndDragRecognizer.start(e);
         this.initialTrim = this.props.trimEnd;
+        e.stopPropagation();
+        e.preventDefault();
     }
     storeRef (el) {
         this.containerElement = el;