Content metadata provider: comment fix

Comment only change. Use "metadata Worker" everywhere, fix grammatical
errors, createError_ is not just used by the Worker, add minor TODO.

Bug: 1114622
Change-Id: I009879b0763c7d33114acfcf1353b713e9924c84
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377331
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Auto-Submit: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801745}

ui/file_manager/file_manager/foreground/js/metadata/content_metadata_provider.js

@@ -67,6 +67,7 @@ class ContentMetadataProvider extends MetadataProvider {
 
     const promises = [];
     for (let i = 0; i < requests.length; i++) {
+      // TODO(crbug.com/1114622): is the .bind actually needed here?
       promises.push(new Promise(((request, fulfill) => {
                                   this.getImpl_(
                                       request.entry, request.names, fulfill);
@@ -76,11 +77,11 @@ class ContentMetadataProvider extends MetadataProvider {
   }
 
   /**
-   * Fetches the metadata.
+   * Fetches the entry metadata.
    * @param {!Entry} entry File entry.
-   * @param {!Array<string>} names Requested metadata type.
-   * @param {function(!MetadataItem)} callback Callback expects metadata value.
-   *     This callback is called asynchronously.
+   * @param {!Array<string>} names Requested metadata types.
+   * @param {function(!MetadataItem)} callback MetadataItem callback. Note
+   *     this callback is called asynchronously.
    * @private
    */
   getImpl_(entry, names, callback) {
@@ -239,7 +240,7 @@ class ContentMetadataProvider extends MetadataProvider {
   }
 
   /**
-   * Handles the 'initialized' message from the metadata reader Worker.
+   * Handles the 'initialized' message from the metadata Worker.
    * @param {RegExp} regexp Regexp of supported urls.
    * @private
    */
@@ -257,7 +258,7 @@ class ContentMetadataProvider extends MetadataProvider {
   }
 
   /**
-   * Handles the 'result' message from the worker.
+   * Handles the 'result' message from the metadata Worker.
    * @param {string} url File url.
    * @param {!MetadataItem} metadataItem The metadata item.
    * @private
@@ -271,7 +272,7 @@ class ContentMetadataProvider extends MetadataProvider {
   }
 
   /**
-   * Handles the 'log' message from the worker.
+   * Handles the 'log' message from the metadata Worker.
    * @param {Array<*>} arglist Log arguments.
    * @private
    */
@@ -284,7 +285,7 @@ class ContentMetadataProvider extends MetadataProvider {
    * Dispatches a message from MediaGalleries API to the appropriate on* method.
    * @param {!Entry} entry File entry.
    * @param {!Object} metadata The metadata from MediaGalleries API.
-   * @return {!Promise<!MetadataItem>}  Promise that resolves with
+   * @return {!Promise<!MetadataItem>} Promise that resolves with the
    *    converted metadata item.
    * @private
    */
@@ -367,9 +368,9 @@ class ContentMetadataProvider extends MetadataProvider {
   }
 
   /**
-   * Handles the 'error' message from the worker.
+   * Returns an 'error' MetadataItem.
    * @param {string} url File entry.
-   * @param {string} step Step failed.
+   * @param {string} step Step that failed.
    * @param {string} errorDescription Error description.
    * @return {!MetadataItem} Error metadata
    * @private
@@ -392,7 +393,7 @@ class ContentMetadataProvider extends MetadataProvider {
 ContentMetadataProvider.Error = class extends Error {
   /**
    * @param {string} url File Entry.
-   * @param {string} step Step failed.
+   * @param {string} step Step that failed.
    * @param {string} errorDescription Error description.
    */
   constructor(url, step, errorDescription) {
@@ -429,7 +430,7 @@ ContentMetadataProvider.PROPERTY_NAMES = [
 ];
 
 /**
- * Path of a worker script.
+ * The metadata Worker script URL.
  * @public @const {string}
  */
 ContentMetadataProvider.WORKER_SCRIPT =