Only allow to lock the mouse when the tab is in fullscreen mode.

content/browser/renderer_host/render_widget_host.h

 // Copyright (c) 2011 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 CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_H_
 #pragma once
 
 #include <deque>
 #include <string>
@@ skipping 450 matching lines @@
   // RenderViewHostDelegate). The gestures that count are 1) any mouse down
   // event and 2) enter or space key presses.
   virtual void OnUserGesture() {}
 
   // Callbacks for notification when the renderer becomes unresponsive to user
   // input events, and subsequently responsive again. RenderViewHost overrides
   // these to tell its delegate to show the user a warning.
   virtual void NotifyRendererUnresponsive() {}
   virtual void NotifyRendererResponsive() {}
 
+  // RenderViewHost overrides this method to impose further restrictions on when
+  // to allow mouse lock. For now, it only allows to lock the mouse when the
+  // current tab is in fullscreen mode.
+  virtual bool CanLockMouse() const;
+
+  void UnlockMouseIfNecessary();
   bool IsMouseLocked() const;
 
  protected:
   // true if a renderer has once been valid. We use this flag to display a sad
   // tab only when we lose our renderer and not if a paint occurs during
   // initialization.
   bool renderer_initialized_;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostTest, Resize);
@@ skipping 246 matching lines @@
 
   std::vector<gfx::PluginWindowHandle> deferred_plugin_handles_;
 
   // The last scroll offset of the render widget.
   gfx::Point last_scroll_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHost);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_H_