Add Panel::SetPanelBoundsInstantly for all platforms.

chrome/browser/ui/panels/panel.cc

Index: chrome/browser/ui/panels/panel.cc
diff --git a/chrome/browser/ui/panels/panel.cc b/chrome/browser/ui/panels/panel.cc
index 5bcab6c969788442fbc6d0a98affc2d27d6fea95..b9c271fc5e237b2b6c051caffdfb06d535c1f4b9 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -78,6 +78,18 @@ void Panel::SetPanelBounds(const gfx::Rect& bounds) {
       content::NotificationService::NoDetails());
 }
 
+void Panel::SetPanelBoundsInstantly(const gfx::Rect& bounds) {
+  if (expansion_state_ == Panel::EXPANDED)
+    restored_size_ = bounds.size();
+
+  native_panel_->SetPanelBoundsInstantly(bounds);
+
+  content::NotificationService::current()->Notify(
+      chrome::NOTIFICATION_PANEL_CHANGED_BOUNDS,
+      content::Source<Panel>(this),
+      content::NotificationService::NoDetails());
+}
+
 void Panel::SetAutoResizable(bool resizable) {
   if (auto_resizable_ == resizable)
     return;