Use strictCheckTypes for image_loader unittests.

 - capture unittest_util.js's use of commandLinePrivate
 - audit remaining things using command_line_private.js unnecessarily
   (Only files in file_manager/common/js and file_manager/foreground/js
    use it directly.)
 - Remove an annoying dep that piex_loader_unittest.js has on webui
   (Use a custom element instead: cr/ui.js dislikes strictCheckTypes.).

Bug: 882750, 879958
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I70c9e16b1ba7b9af64e0ce01b7177ef02500c948
Reviewed-on: https://chromium-review.googlesource.com/1245079
Commit-Queue: Trent Apted <tapted@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594945}

ui/file_manager/audio_player/js/BUILD.gn

@@ -18,7 +18,6 @@ js_library("closure_compile_externs") {
   sources = []
   externs_list = [
     "$externs_path/chrome_extensions.js",
-    "$externs_path/command_line_private.js",
     "$externs_path/metrics_private.js",
     "../../externs/audio_player_foreground.js",
     "../../externs/entry_location.js",

ui/file_manager/file_manager/background/js/BUILD.gn

@@ -55,7 +55,6 @@ js_type_check("closure_compile") {
 js_library("closure_compile_externs") {
   sources = []
   externs_list = [
-    "$externs_path/command_line_private.js",
     "$externs_path/metrics_private.js",
     "../../../externs/background/file_browser_background.js",
     "../../../externs/background/file_browser_background_full.js",

ui/file_manager/file_manager/common/js/BUILD.gn

@@ -101,6 +101,7 @@ js_library("unittest_util") {
   deps = [
     "//ui/webui/resources/js:webui_resource_test",
   ]
+  externs_list = [ "$externs_path/command_line_private.js" ]
 }
 
 js_library("util") {

ui/file_manager/file_manager/common/js/unittest_util.js

@@ -12,12 +12,14 @@ var INTERVAL_FOR_WAIT_UNTIL = 100; // ms
  *     test failed.
  */
 function reportPromise(promise, callback) {
-  promise.then(function() {
-    callback(/* error */ false);
-  }, function(error) {
-    console.error(error.stack || error);
-    callback(/* error */ true);
-  });
+  promise.then(
+      function() {
+        callback(/* error */ false);
+      },
+      function(/** @type {Error} */ error) {
+        console.error(error.stack || error);
+        callback(/* error */ true);
+      });
 }
 
 /**

ui/file_manager/file_manager/foreground/js/metadata/BUILD.gn

@@ -38,7 +38,6 @@ js_type_check("closure_compile") {
 js_library("closure_compile_externs") {
   sources = []
   externs_list = [
-    "$externs_path/command_line_private.js",
     "../../../../externs/app_window_common.js",
     "../../../../externs/entry_location.js",
     "../../../../externs/platform.js",

ui/file_manager/file_manager/foreground/js/ui/BUILD.gn

@@ -45,7 +45,6 @@ js_type_check("closure_compile") {
 js_library("closure_compile_externs") {
   sources = []
   externs_list = [
-    "$externs_path/command_line_private.js",
     "$externs_path/metrics_private.js",
     "$externs_path/web_animations.js",
     "../../../../externs/app_window_common.js",

ui/file_manager/image_loader/BUILD.gn

@@ -102,7 +102,6 @@ js_library("piex_loader_unittest") {
     ":piex_loader",
     "../file_manager/common/js:unittest_util",
     "//ui/webui/resources/js:webui_resource_test",
-    "//ui/webui/resources/js/cr:ui",
   ]
 }
 
@@ -126,8 +125,7 @@ js_library("scheduler") {
 }
 
 js_unit_tests("unit_tests") {
-  # TODO(tapted): Uncomment the next line.
-  # closure_flags = default_closure_args + [ "jscomp_error=strictCheckTypes" ]
+  closure_flags = default_closure_args + [ "jscomp_error=strictCheckTypes" ]
   deps = [
     ":cache_unittest",
     ":image_loader_client_unittest",

ui/file_manager/image_loader/piex_loader_unittest.js

@@ -8,36 +8,37 @@ chrome.fileManagerPrivate = {
   }
 };
 
-/**
- * @constructor
- * @extends {HTMLDivElement}
- */
-var MockModule = /** @type{function(new:MockModule)}*/ (cr.ui.define('div'));
-MockModule.prototype = Object.create(HTMLDivElement.prototype);
-MockModule.prototype.constructor = MockModule;
+class MockModule extends HTMLDivElement {
+  constructor() {
+    super();
+    /** @type{?function()} */
+    this.onBeforeMessageCallback_ = null;
+    setTimeout(() => {
+      this.dispatchEvent(new Event('load', {bubbles: true}));
+    });
+  }
 
-MockModule.prototype.setBeforeMessageCallback = function(callback) {
-  this.onBeforeMessageCallback_ = callback;
-};
+  setBeforeMessageCallback(callback) {
+    this.onBeforeMessageCallback_ = callback;
+  }
 
-MockModule.prototype.decorate = function() {
-  this.onBeforeMessageCallback_ = null;
-  setTimeout(function() {
-    this.dispatchEvent(new Event('load', {bubbles: true}));
-  }.bind(this));
-};
+  postMessage(message) {
+    setTimeout(() => {
+      this.dispatchEvent(new Event('load', {bubbles: true}));
+      if (this.onBeforeMessageCallback_)
+        this.onBeforeMessageCallback_();
 
-MockModule.prototype.postMessage = function(message) {
-  setTimeout(function() {
-    this.dispatchEvent(new Event('load', {bubbles: true}));
-    if (this.onBeforeMessageCallback_)
-      this.onBeforeMessageCallback_();
+      let e = new Event('message', {bubbles: true});
+      // Cast to a MessageEvent to write to |data|. We can't use
+      // `new MessageEvent` since its |data| property is read-only.
+      /** @type{MessageEvent} */ (e)
+          .data = {id: message.id, thumbnail: 'thumbnail-data', orientation: 1};
+      this.dispatchEvent(e);
+    });
+  }
+}
 
-    var e = new CustomEvent('message', {bubbles: true});
-    e.data = {id: message.id, thumbnail: 'thumbnail-data', orientation: 1};
-    this.dispatchEvent(e);
-  }.bind(this));
-};
+customElements.define('mock-module', MockModule, {extends: 'div'});
 
 function testUnloadingAfterTimeout(callback) {
   var loadCount = 0;

ui/file_manager/video_player/js/BUILD.gn

@@ -20,7 +20,6 @@ js_library("closure_compile_externs") {
   sources = []
   externs_list = [
     "$externs_path/chrome_extensions.js",
-    "$externs_path/command_line_private.js",
     "$externs_path/media_player_private.js",
     "$externs_path/metrics_private.js",
     "../../externs/chrome_cast.js",

ui/file_manager/video_player/js/cast/BUILD.gn

@@ -18,7 +18,6 @@ js_library("closure_compile_externs") {
   sources = []
   externs_list = [
     "$externs_path/chrome_extensions.js",
-    "$externs_path/command_line_private.js",
     "$externs_path/media_player_private.js",
     "$externs_path/metrics_private.js",
     "../../../externs/app_window_common.js",