Support getEntryId for entries passed to apps as launch data.

chrome/test/data/extensions/platform_apps/launch_file_with_no_extension/test.js

Index: chrome/test/data/extensions/platform_apps/launch_file_with_no_extension/test.js
diff --git a/chrome/test/data/extensions/platform_apps/launch_file_with_no_extension/test.js b/chrome/test/data/extensions/platform_apps/launch_file_with_no_extension/test.js
index 211b2d51bb7d09cda2914aca84987f022a125eae..7538174e11460ff222ce820c2b85af643d874f9b 100644
--- a/chrome/test/data/extensions/platform_apps/launch_file_with_no_extension/test.js
+++ b/chrome/test/data/extensions/platform_apps/launch_file_with_no_extension/test.js
@@ -10,6 +10,8 @@ chrome.app.runtime.onLaunched.addListener(function (launchData) {
       chrome.test.assertEq(launchData.id, "text",
           "launchData.id incorrect");
       chrome.test.assertEq(launchData.items.length, 1);
+      chrome.test.assertTrue(
+          chrome.fileSystem.getEntryId(launchData.items[0].entry) != null);
 
       launchData.items[0].entry.file(function(file) {
         var reader = new FileReader();