avoid layout recalculation upon scrollport resize

lib/hterm.js

@@ -324,6 +324,25 @@ hterm.Terminal.prototype.onMouseDown_ = function (e) {
   }
 };
 
+// override `ScrollPort.resize` to avoid an expensive calculation
+// just to get the size of the scrollbar, which for Hyper is always
+// set to overlay (hence with `0`)
+hterm.ScrollPort.prototype.resize = function () {
+  this.currentScrollbarWidthPx = 0;
+
+  this.syncScrollHeight();
+  this.syncRowNodesDimensions_();
+
+  this.publish(
+    'resize',
+    {scrollPort: this},
+    () => {
+      this.scrollRowToBottom(this.rowProvider_.getRowCount());
+      this.scheduleRedraw();
+    }
+  );
+};
+
 // make background transparent to avoid transparency issues
 hterm.ScrollPort.prototype.setBackgroundColor = function () {
   this.screen_.style.backgroundColor = 'transparent';