Implement ShowMenu for StubRecoveryUI

The ShowMenu in StubRecoveryUI used to return initial selection
immediately. This leads to an immediate reboot if we enter recovery
with a stub UI and wait for user's input. This cl changes the behavior
of stub UI's ShowMenu so that it waits keys in loop, and only returns in
the case of interruption or time out.

Bug: 130535924
Test: start recovery with a stub UI, wait for the timeout
Change-Id: I96ad8aad8930756b09101bb98ba5fbe7b53bcb37

recovery_ui/Android.bp

@@ -23,6 +23,7 @@ cc_library {
     srcs: [
         "device.cpp",
         "screen_ui.cpp",
+        "stub_ui.cpp",
         "ui.cpp",
         "vr_ui.cpp",
         "wear_ui.cpp",

recovery_ui/include/recovery_ui/stub_ui.h

@@ -62,11 +62,9 @@ class StubRecoveryUI : public RecoveryUI {
 
   // menu display
   size_t ShowMenu(const std::vector<std::string>& /* headers */,
-                  const std::vector<std::string>& /* items */, size_t initial_selection,
+                  const std::vector<std::string>& /* items */, size_t /* initial_selection */,
                   bool /* menu_only */,
-                  const std::function<int(int, bool)>& /* key_handler */) override {
+                  const std::function<int(int, bool)>& /* key_handler */) override;
-    return initial_selection;
-  }
 
   size_t ShowPromptWipeDataMenu(const std::vector<std::string>& /* backup_headers */,
                                 const std::vector<std::string>& /* backup_items */,

recovery_ui/stub_ui.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "recovery_ui/stub_ui.h"
+
+#include <android-base/logging.h>
+
+#include "recovery_ui/device.h"
+
+size_t StubRecoveryUI::ShowMenu(const std::vector<std::string>& /* headers */,
+                                const std::vector<std::string>& /* items */,
+                                size_t /* initial_selection */, bool /* menu_only */,
+                                const std::function<int(int, bool)>& /*key_handler*/) {
+  while (true) {
+    int key = WaitKey();
+    // Exit the loop in the case of interruption or time out.
+    if (key == static_cast<int>(KeyError::INTERRUPTED) ||
+        key == static_cast<int>(KeyError::TIMED_OUT)) {
+      return static_cast<size_t>(key);
+    }
+  }
+  LOG(FATAL) << "Unreachable key selected in ShowMenu of stub UI";
+}