Allow panels to be created as detached panels.

chrome/browser/ui/panels/detached_panel_strip.h

Index: chrome/browser/ui/panels/detached_panel_strip.h
diff --git a/chrome/browser/ui/panels/detached_panel_strip.h b/chrome/browser/ui/panels/detached_panel_strip.h
index 51fd2a2f7ecb42b3a1ae443cca837fb37d4062fc..d7560f9a7ea02c24cfca433d1175d7084ef43938 100644
--- a/chrome/browser/ui/panels/detached_panel_strip.h
+++ b/chrome/browser/ui/panels/detached_panel_strip.h
@@ -65,7 +65,15 @@ class DetachedPanelStrip : public PanelStrip {
   int num_panels() const { return panels_.size(); }
   const Panels& panels() const { return panels_; }
 
+  // Returns default top-left to use for a detached panel whose position is
+  // not specified during panel creation.
+  gfx::Point GetDefaultPanelOrigin();
+
  private:
+  // Offset the default panel top-left position by kPanelTilePixels. Wrap
+  // around to initial position if position goes beyond display area.
+  void ComputeNextDefaultPanelOrigin();
+
   struct PanelPlacement {
     Panel* panel;
     gfx::Point position;
@@ -84,6 +92,10 @@ class DetachedPanelStrip : public PanelStrip {
   // Used to save the placement information for a panel.
   PanelPlacement saved_panel_placement_;
 
+  // Default top-left position to use for next detached panel if position is
+  // unspecified by panel creator.
+  gfx::Point default_panel_origin_;
+
   DISALLOW_COPY_AND_ASSIGN(DetachedPanelStrip);
 };