Add power-user keyboard mode for ChromeOS with Search key acting as a typical Fn key.

chrome/browser/ui/ash/event_rewriter.h

Index: chrome/browser/ui/ash/event_rewriter.h
diff --git a/chrome/browser/ui/ash/event_rewriter.h b/chrome/browser/ui/ash/event_rewriter.h
index 1d01ed4a2695a9250a45fb2a6341d7d48b40bdc5..49f76e5ac48b4006eb2287a99edd8e1860f18b09 100644
--- a/chrome/browser/ui/ash/event_rewriter.h
+++ b/chrome/browser/ui/ash/event_rewriter.h
@@ -95,7 +95,8 @@ class EventRewriter : public ash::EventRewriterDelegate,
 #endif
 
   // Rewrites the |event| by applying all RewriteXXX functions as needed.
-  void Rewrite(ui::KeyEvent* event);
+  // Returns whether the event should be rewritten or dropped.
+  ash::EventRewriterDelegate::Action Rewrite(ui::KeyEvent* event);
 
   // Rewrites a modifier key press/release following the current user
   // preferences.
@@ -116,8 +117,21 @@ class EventRewriter : public ash::EventRewriterDelegate,
   //  * Alt+Down -> Next (aka PageDown)
   //  * Ctrl+Alt+Up -> Home
   //  * Ctrl+Alt+Down -> End
+  // When the Search key acts as a function key, it instead maps:
+  //  * Search+Backspace -> Delete
+  //  * Search+Up -> Prior (aka PageUp)
+  //  * Search+Down -> Next (aka PageDown)
+  //  * Search+Left -> Home
+  //  * Search+right -> End
+  // Returns true when the |event| is rewritten.
   bool RewriteBackspaceAndArrowKeys(ui::KeyEvent* event);
 
+#if defined(OS_CHROMEOS)
+  // When the Search key acts as a function key, it drops Search key presses,
+  // and drops the release as well if any key is pressed while Search was down.
+  bool DropSearchKey(ui::KeyEvent* event);
+#endif
+
   // Rewrites the located |event|.
   void RewriteLocatedEvent(ui::LocatedEvent* event);
 
@@ -146,6 +160,8 @@ class EventRewriter : public ash::EventRewriterDelegate,
   int last_device_id_;
 
 #if defined(OS_CHROMEOS)
+  bool drop_search_key_release_;
+
   // X keycodes corresponding to various keysyms.
   unsigned int control_l_xkeycode_;
   unsigned int control_r_xkeycode_;