[AudioPlayer] Add test for opening another file from Files.app

chrome/test/data/extensions/api_test/file_manager_browsertest/background.js

Index: chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
diff --git a/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js b/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
index 33fd18e54d66a94b64ff7aa6d40a9eea551d7d18..b07b3f30a2939cf4246e3d49857def85f0b1d733 100644
--- a/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
+++ b/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
@@ -115,8 +115,8 @@ function repeatUntil(checkFunction) {
 
 /**
  * Waits until a window having the given ID prefix appears.
- * @param {string} appIdPrefix ID prefix of the requested window.
- * @param {Promise} promise Promise to be fulfilled with a found window's ID.
+ * @param {string} windowIdPrefix ID prefix of the requested window.
+ * @return {Promise} promise Promise to be fulfilled with a found window's ID.
  */
 function waitForWindow(windowIdPrefix) {
   return repeatUntil(function() {
@@ -131,6 +131,40 @@ function waitForWindow(windowIdPrefix) {
 }
 
 /**
+ * Closes a window and waits until the window is closed.
+ *
+ * @param {string} windowId ID of the window to close.
+ * @return {Promise} promise Promise to be fulfilled with the result (true:
+ *     success, false: failed).
+ */
+function closeWindowAndWait(windowId) {
+  // Closes the window.
+  return callRemoteTestUtil('closeWindow', null, [windowId]).then(
+      function(result) {
+        // Returns false when the closing is failed.
+        if (!result)
+          return false;
+
+        return repeatUntil(function() {
+          return callRemoteTestUtil('getWindows', null, []).then(
+              function(windows) {
+                for (var id in windows) {
+                  if (id === windowId) {
+                    // Window is still available. Continues waiting.
+                    return pending('Window with the prefix %s is not found.',
+                                   windowId);
+                  }
+                }
+                // Window is not available. Closing is done successfully.
+                return true;
+              }
+          );
+        });
+      }
+  );
+}
+
+/**
  * Waits until the window turns to the given size.
  * @param {string} windowId Target window ID.
  * @param {number} width Requested width in pixels.