Adds functionality to anchor widgets to the top-of-window views in immersive mode

chrome/browser/ui/views/frame/immersive_mode_controller.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_FRAME_IMMERSIVE_MODE_CONTROLLER_H_
 #define CHROME_BROWSER_UI_VIEWS_FRAME_IMMERSIVE_MODE_CONTROLLER_H_
 
 #include "base/compiler_specific.h"
 
 class BrowserView;
 
+namespace views {
+class Widget;
+}
+
 // Controller for an "immersive mode" similar to MacOS presentation mode where
 // the top-of-window views are hidden until the mouse hits the top of the
 // screen. The tab strip is optionally painted with miniature "tab indicator"
 // rectangles.
 // Currently, immersive mode is only available for Chrome OS.
 class ImmersiveModeController {
  public:
   // Base class for a lock which keeps the top-of-window views revealed for the
   // duration of its lifetime. See GetRevealedLock() for more details.
   class RevealedLock {
@@ skipping 26 matching lines @@
 
   // Returns a lock which will keep the top-of-window views revealed for its
   // lifetime. Several locks can be obtained. When all of the locks are
   // destroyed, if immersive mode is enabled and there is nothing else keeping
   // the top-of-window views revealed, the top-of-window views will be closed.
   // This method always returns a valid lock regardless of whether immersive
   // mode is enabled. The lock's lifetime can span immersive mode being
   // enabled / disabled.
   // The caller takes ownership of the returned lock.
   virtual RevealedLock* GetRevealedLock() WARN_UNUSED_RESULT = 0;
+
+  // Anchor |widget| to the top-of-window views. This repositions |widget| such
+  // that it stays |y_offset| below the top-of-window views when the
+  // top-of-window views are animating (top-of-window views reveal / unreveal)
+  // or the top container's bounds change (eg the bookmark bar is shown).
+  // If the top-of-window views are revealed (or become revealed), |widget|
+  // will keep the top-of-window views revealed till either |widget| is hidden
+  // or UnanchorWidgetFromTopContainer() is called.
+  // It is legal for a widget to be anchored when immersive fullscreen is
+  // disabled, however it will have no effect till immersive fullscreen is
+  // enabled.
+  virtual void AnchorWidgetToTopContainer(views::Widget* widget,
+                                          int y_offset) = 0;
+
+  // Stops managing |widget|'s y position.
+  // Closes the top-of-window views if no locks or other anchored widgets are
+  // keeping the top-of-window views revealed.
+  virtual void UnanchorWidgetFromTopContainer(views::Widget* widget) = 0;
+
+  // Called by the TopContainerView to indicate that its bounds have changed.
+  virtual void OnTopContainerBoundsChanged() = 0;
 };
 
 namespace chrome {
 
 // Returns true if immersive mode should be used for fullscreen based on
 // command line flags.
 // Implemented in immersive_mode_controller_factory.cc.
 bool UseImmersiveFullscreen();
 
 // Implemented in immersive_mode_controller_factory.cc.
 ImmersiveModeController* CreateImmersiveModeController();
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_VIEWS_FRAME_IMMERSIVE_MODE_CONTROLLER_H_