Panels test cleanup.

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 b8a2790deb6e5792aa232db996e3ab54c1c76e2d..ac995394bfeebeb01ec39b4da3c441bad5c0c070 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -506,9 +506,17 @@ void Panel::OnContentsAutoResized(const gfx::Size& new_content_size) {
   if (!panel_strip_)
     return;
 
-  panel_strip_->ResizePanelWindow(
-      this,
-      native_panel_->WindowSizeFromContentSize(new_content_size));
+  gfx::Size new_window_size =
+      native_panel_->WindowSizeFromContentSize(new_content_size);
+
+  // Ignore content auto resizes until window frame size is known.
+  // This reduces extra resizes when panel is first shown.
+  // After window frame size is known, it will trigger another content
+  // auto resize.
+  if (new_content_size == new_window_size)
+    return;
+
+  panel_strip_->ResizePanelWindow(this, new_window_size);
 }
 
 void Panel::OnWindowResizedByMouse(const gfx::Rect& new_bounds) {