Support dragging panels to stack and snap.

chrome/browser/ui/views/panels/panel_view.cc

Index: chrome/browser/ui/views/panels/panel_view.cc
diff --git a/chrome/browser/ui/views/panels/panel_view.cc b/chrome/browser/ui/views/panels/panel_view.cc
index b99dcb419bb4388ba7a2ef83661270ce90aa2701..cfcc1e110f62404b60dee1bc3738eb358c3c89f0 100644
--- a/chrome/browser/ui/views/panels/panel_view.cc
+++ b/chrome/browser/ui/views/panels/panel_view.cc
@@ -13,6 +13,7 @@
 #include "chrome/browser/ui/panels/panel.h"
 #include "chrome/browser/ui/panels/panel_bounds_animation.h"
 #include "chrome/browser/ui/panels/panel_manager.h"
+#include "chrome/browser/ui/panels/stacked_panel_collection.h"
 #include "chrome/browser/ui/views/panels/panel_frame_view.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/render_widget_host_view.h"
@@ -582,6 +583,29 @@ int PanelView::TitleOnlyHeight() const {
   return panel::kTitlebarHeight;
 }
 
+void PanelView::UpdatePanelStackingProperty() {
+#if defined(OS_WIN) && !defined(USE_AURA)
+  // In order for a panel stack that holds multiple panels to appear as a single
+  // window on the taskbar or launcher, the owner window of this panel view
+  // should be set to the panel stack window. In addition, the extended style
+  // WS_EX_APPWINDOW, that is used to force a top-level window onto the taskbar,
+  // should be cleared.
+  StackedPanelCollection* stack = NULL;
+  if (panel_->collection()->type() == PanelCollection::STACKED)
+    stack = static_cast<StackedPanelCollection*>(panel_->collection());
+  HWND owner = stack ? stack->GetNativeWindow() : NULL;
+  if (owner)
+    UpdateWindowAttribute(GWL_EXSTYLE, 0, WS_EX_APPWINDOW, false);
+  else
+    UpdateWindowAttribute(GWL_EXSTYLE, WS_EX_APPWINDOW, 0, false);
+  ::SetWindowLong(GetNativePanelHandle(),
+                  GWL_HWNDPARENT,
+                  reinterpret_cast<LONG>(owner));
+#else
+  NOTIMPLEMENTED();
+#endif
+}
+
 void PanelView::AttachWebContents(content::WebContents* contents) {
   web_view_->SetWebContents(contents);
 }