Support dragging panels to stack and snap.

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 35900ca68d4845adbbeb4120fc7f36f96116905f..26c1606bb833c110e488854676d01e67e89cfce1 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -25,6 +25,7 @@
 #include "chrome/browser/ui/panels/panel_collection.h"
 #include "chrome/browser/ui/panels/panel_host.h"
 #include "chrome/browser/ui/panels/panel_manager.h"
+#include "chrome/browser/ui/panels/stacked_panel_collection.h"
 #include "chrome/browser/web_applications/web_app.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/extensions/extension.h"
@@ -245,6 +246,11 @@ const std::string Panel::extension_id() const {
   return web_app::GetExtensionIdFromApplicationName(app_name_);
 }
 
+StackedPanelCollection* Panel::stack() const {
+  return collection_ && collection_->type() == PanelCollection::STACKED ?
+      static_cast<StackedPanelCollection*>(collection_) : NULL;
+}
+
 content::WebContents* Panel::GetWebContents() const {
   return panel_host_.get() ? panel_host_->web_contents() : NULL;
 }
@@ -809,6 +815,12 @@ void Panel::WebContentsFocused(content::WebContents* contents) {
   native_panel_->PanelWebContentsFocused(contents);
 }
 
+void Panel::MoveByInstantly(const gfx::Vector2d& delta_origin) {
+  gfx::Rect bounds = GetBounds();
+  bounds.Offset(delta_origin);
+  SetPanelBoundsInstantly(bounds);
+}
+
 const extensions::Extension* Panel::GetExtension() const {
   ExtensionService* extension_service =
       extensions::ExtensionSystem::Get(profile())->extension_service();