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

ash/accelerators/accelerator_controller.cc

Index: ash/accelerators/accelerator_controller.cc
diff --git a/ash/accelerators/accelerator_controller.cc b/ash/accelerators/accelerator_controller.cc
index f6199cc4e3024597da006da8b2c15bc9c4db337e..493e2bfc54b12cfd6e6ccc16a67e94d8f2c261f2 100644
--- a/ash/accelerators/accelerator_controller.cc
+++ b/ash/accelerators/accelerator_controller.cc
@@ -534,6 +534,15 @@ bool AcceleratorController::PerformAction(int action,
       // this key combination is reserved for partial screenshot.
       return true;
     case TOGGLE_APP_LIST:
+      // See: case NEXT_IME.
+      if (previous_event_type == ui::ET_KEY_RELEASED ||
+          // The LWIN binding is on release. If something else was pressed since
+          // the LWIN key, then we should ignore the release of LWIN.
+          (accelerator.type() == ui::ET_KEY_RELEASED &&
+           context_.previous_accelerator().key_code() != ui::VKEY_LWIN)) {
+        // We totally ignore this accelerator.
+        return false;
+      }
       if (key_code == ui::VKEY_LWIN && shell->delegate())
         shell->delegate()->RecordUserMetricsAction(UMA_ACCEL_SEARCH_LWIN);
       // When spoken feedback is enabled, we should neither toggle the list nor