Support detaching/attaching panels via inter-strip drags.

chrome/browser/ui/panels/panel_browser_view.cc

Index: chrome/browser/ui/panels/panel_browser_view.cc
diff --git a/chrome/browser/ui/panels/panel_browser_view.cc b/chrome/browser/ui/panels/panel_browser_view.cc
index ab24051d24d067fff98ff44496cbadcff145924e..e82f2c00b34dead422043b9cc00d0b349e3192ff 100644
--- a/chrome/browser/ui/panels/panel_browser_view.cc
+++ b/chrome/browser/ui/panels/panel_browser_view.cc
@@ -542,19 +542,26 @@ bool PanelBrowserView::EndDragging(bool cancelled) {
 void PanelBrowserView::SetPanelAppIconVisibility(bool visible) {
 #if defined(OS_WIN) && !defined(USE_AURA)
   gfx::NativeWindow native_window = GetNativeHandle();
-  ::ShowWindow(native_window, SW_HIDE);
   int style = ::GetWindowLong(native_window, GWL_EXSTYLE);
+  int new_style = style;
   if (visible)
-    style &= (~WS_EX_TOOLWINDOW);
+    new_style &= (~WS_EX_TOOLWINDOW);
   else
-    style |= WS_EX_TOOLWINDOW;
-  ::SetWindowLong(native_window, GWL_EXSTYLE, style);
-  ::ShowWindow(native_window, SW_SHOWNA);
+    new_style |= WS_EX_TOOLWINDOW;
+  if (style != new_style) {
+    ::ShowWindow(native_window, SW_HIDE);
+    ::SetWindowLong(native_window, GWL_EXSTYLE, new_style);
+    ::ShowWindow(native_window, SW_SHOWNA);
+  }
 #else
   NOTIMPLEMENTED();
 #endif
 }
 
+void PanelBrowserView::SetPanelAlwaysOnTop(bool on_top) {
+  GetWidget()->SetAlwaysOnTop(on_top);
+}
+
 // NativePanelTesting implementation.
 class NativePanelTestingWin : public NativePanelTesting {
  public: