Add an experimental keyboard lock, where Esc must be held to exit.

chrome/browser/ui/exclusive_access/exclusive_access_manager.h

Index: chrome/browser/ui/exclusive_access/exclusive_access_manager.h
diff --git a/chrome/browser/ui/exclusive_access/exclusive_access_manager.h b/chrome/browser/ui/exclusive_access/exclusive_access_manager.h
index dae8b55db34bb6333ee9ae64c4d31636000f9717..567638f3b4e6902b183be83138e7781512da0bd3 100644
--- a/chrome/browser/ui/exclusive_access/exclusive_access_manager.h
+++ b/chrome/browser/ui/exclusive_access/exclusive_access_manager.h
@@ -8,6 +8,7 @@
 #include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/timer/timer.h"
 #include "chrome/browser/ui/exclusive_access/exclusive_access_bubble_type.h"
 #include "chrome/browser/ui/exclusive_access/fullscreen_controller.h"
 #include "chrome/browser/ui/exclusive_access/mouse_lock_controller.h"
@@ -46,6 +47,7 @@ class ExclusiveAccessManager {
 
   GURL GetExclusiveAccessBubbleURL() const;
 
+  static bool IsExperimentalKeyboardLockUIEnabled();
   static bool IsSimplifiedFullscreenUIEnabled();
 
   // Callbacks ////////////////////////////////////////////////////////////////
@@ -72,9 +74,13 @@ class ExclusiveAccessManager {
   void RecordBubbleReshownUMA(ExclusiveAccessBubbleType type);
 
  private:
+  // Called when the user has held down Escape.
+  void HandleUserHeldEscape();
+
   ExclusiveAccessContext* const exclusive_access_context_;
   FullscreenController fullscreen_controller_;
   MouseLockController mouse_lock_controller_;
+  base::OneShotTimer hold_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(ExclusiveAccessManager);
 };