Stick windows to sides of workspaces

ash/display/screen_position_controller.cc

Index: ash/display/screen_position_controller.cc
diff --git a/ash/display/screen_position_controller.cc b/ash/display/screen_position_controller.cc
index ef2d2518d05f3a1ac957c438bf42434161175951..ffd3f1900d78701a830a7835407cf7807de49e8e 100644
--- a/ash/display/screen_position_controller.cc
+++ b/ash/display/screen_position_controller.cc
@@ -162,6 +162,10 @@ void ScreenPositionController::SetBounds(aura::Window* window,
     aura::Window* dst_container = NULL;
     if (dst_root != window->GetRootWindow()) {
       int container_id = window->parent()->id();
+      // Dragging a docked window to another root window should show it floating
+      // rather than docked in another screen's dock.
+      if (container_id == kShellWindowId_DockContainer)
+        container_id = kShellWindowId_WorkspaceContainer;
       // All containers that uses screen coordinates must have valid window ids.
       DCHECK_GE(container_id, 0);
       // Don't move modal background.