Remove some platform specific stuff from views.

ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js

Index: ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js
diff --git a/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js b/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js
deleted file mode 100644
index 8de5921ed121113198be5350a54a533484ce1f31..0000000000000000000000000000000000000000
--- a/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js
+++ /dev/null
@@ -1,1111 +0,0 @@
-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-'use strict';
-
-/**
- * MetadataCache is a map from Entry to an object containing properties.
- * Properties are divided by types, and all properties of one type are accessed
- * at once.
- * Some of the properties:
- * {
- *   filesystem: size, modificationTime
- *   internal: presence
- *   external: pinned, present, hosted, availableOffline
- *
- *   Following are not fetched for non-present external files.
- *   media: artist, album, title, width, height, imageTransform, etc.
- *   thumbnail: url, transform
- *
- *   Following are always fetched from content, and so force the downloading
- *   of external files. One should use this for required content metadata,
- *   i.e. image orientation.
- *   fetchedMedia: width, height, etc.
- * }
- *
- * Typical usages:
- * {
- *   cache.get([entry1, entry2], 'external|filesystem', function(metadata) {
- *     if (metadata[0].external.pinned && metadata[1].filesystem.size === 0)
- *       alert("Pinned and empty!");
- *   });
- *
- *   cache.set(entry, 'internal', {presence: 'deleted'});
- *
- *   cache.clear([fileEntry1, fileEntry2], 'filesystem');
- *
- *   // Getting fresh value.
- *   cache.clear(entry, 'thumbnail');
- *   cache.getOne(entry, 'thumbnail', function(thumbnail) {
- *     img.src = thumbnail.url;
- *   });
- *
- *   var cached = cache.getCached(entry, 'filesystem');
- *   var size = (cached && cached.size) || UNKNOWN_SIZE;
- * }
- *
- * @param {Array.<MetadataProvider>} providers Metadata providers.
- * @constructor
- */
-function MetadataCache(providers) {
-  /**
-   * Map from Entry (using Entry.toURL) to metadata. Metadata contains
-   * |properties| - an hierarchical object of values, and an object for each
-   * metadata provider: <prodiver-id>: {time, callbacks}
-   * @private
-   */
-  this.cache_ = {};
-
-  /**
-   * List of metadata providers.
-   * @private
-   */
-  this.providers_ = providers;
-
-  /**
-   * List of observers added. Each one is an object with fields:
-   *   re - regexp of urls;
-   *   type - metadata type;
-   *   callback - the callback.
-   * @private
-   */
-  this.observers_ = [];
-  this.observerId_ = 0;
-
-  this.batchCount_ = 0;
-  this.totalCount_ = 0;
-
-  this.currentCacheSize_ = 0;
-
-  /**
-   * Time of first get query of the current batch. Items updated later than this
-   * will not be evicted.
-   *
-   * @type {Date}
-   * @private
-   */
-  this.lastBatchStart_ = new Date();
-
-  Object.seal(this);
-}
-
-/**
- * Observer type: it will be notified if the changed Entry is exactly the same
- * as the observed Entry.
- */
-MetadataCache.EXACT = 0;
-
-/**
- * Observer type: it will be notified if the changed Entry is an immediate child
- * of the observed Entry.
- */
-MetadataCache.CHILDREN = 1;
-
-/**
- * Observer type: it will be notified if the changed Entry is a descendant of
- * of the observer Entry.
- */
-MetadataCache.DESCENDANTS = 2;
-
-/**
- * Margin of the cache size. This amount of caches may be kept in addition.
- */
-MetadataCache.EVICTION_THRESHOLD_MARGIN = 500;
-
-/**
- * @param {VolumeManagerWrapper} volumeManager Volume manager instance.
- * @return {MetadataCache!} The cache with all providers.
- */
-MetadataCache.createFull = function(volumeManager) {
-  // ExternalProvider should be prior to FileSystemProvider, because it covers
-  // FileSystemProvider for files on the external backend, eg. Drive.
-  return new MetadataCache([
-    new ExternalProvider(volumeManager),
-    new FilesystemProvider(),
-    new ContentProvider()
-  ]);
-};
-
-/**
- * Clones metadata entry. Metadata entries may contain scalars, arrays,
- * hash arrays and Date object. Other objects are not supported.
- * @param {Object} metadata Metadata object.
- * @return {Object} Cloned entry.
- */
-MetadataCache.cloneMetadata = function(metadata) {
-  if (metadata instanceof Array) {
-    var result = [];
-    for (var index = 0; index < metadata.length; index++) {
-      result[index] = MetadataCache.cloneMetadata(metadata[index]);
-    }
-    return result;
-  } else if (metadata instanceof Date) {
-    var result = new Date();
-    result.setTime(metadata.getTime());
-    return result;
-  } else if (metadata instanceof Object) {  // Hash array only.
-    var result = {};
-    for (var property in metadata) {
-      if (metadata.hasOwnProperty(property))
-        result[property] = MetadataCache.cloneMetadata(metadata[property]);
-    }
-    return result;
-  } else {
-    return metadata;
-  }
-};
-
-/**
- * @return {boolean} Whether all providers are ready.
- */
-MetadataCache.prototype.isInitialized = function() {
-  for (var index = 0; index < this.providers_.length; index++) {
-    if (!this.providers_[index].isInitialized()) return false;
-  }
-  return true;
-};
-
-/**
- * Changes the size of cache by delta value. The actual cache size may be larger
- * than the given value.
- *
- * @param {number} delta The delta size to be changed the cache size by.
- */
-MetadataCache.prototype.resizeBy = function(delta) {
-  this.currentCacheSize_ += delta;
-  if (this.currentCacheSize_ < 0)
-    this.currentCacheSize_ = 0;
-
-  if (this.totalCount_ > this.currentEvictionThreshold_())
-    this.evict_();
-};
-
-/**
- * Returns the current threshold to evict caches. When the number of caches
- * exceeds this, the cache should be evicted.
- * @return {number} Threshold to evict caches.
- * @private
- */
-MetadataCache.prototype.currentEvictionThreshold_ = function() {
-  return this.currentCacheSize_ * 2 + MetadataCache.EVICTION_THRESHOLD_MARGIN;
-};
-
-/**
- * Fetches the metadata, puts it in the cache, and passes to callback.
- * If required metadata is already in the cache, does not fetch it again.
- *
- * @param {Array.<Entry>} entries The list of entries.
- * @param {string} type The metadata type.
- * @param {function(Object)} callback The metadata is passed to callback.
- *     The callback is called asynchronously.
- */
-MetadataCache.prototype.get = function(entries, type, callback) {
-  this.getInternal_(entries, type, false, callback);
-};
-
-/**
- * Fetches the metadata, puts it in the cache, and passes to callback.
- * Even if required metadata is already in the cache, fetches it again.
- *
- * @param {Array.<Entry>} entries The list of entries.
- * @param {string} type The metadata type.
- * @param {function(Object)} callback The metadata is passed to callback.
- *     The callback is called asynchronously.
- */
-MetadataCache.prototype.getLatest = function(entries, type, callback) {
-  this.getInternal_(entries, type, true, callback);
-};
-
-/**
- * Fetches the metadata, puts it in the cache. This is only for internal use.
- *
- * @param {Array.<Entry>} entries The list of entries.
- * @param {string} type The metadata type.
- * @param {boolean} refresh True to get the latest value and refresh the cache,
- *     false to get the value from the cache.
- * @param {function(Object)} callback The metadata is passed to callback.
- *     The callback is called asynchronously.
- * @private
- */
-MetadataCache.prototype.getInternal_ =
-    function(entries, type, refresh, callback) {
-  if (entries.length === 0) {
-    if (callback) setTimeout(callback.bind(null, []), 0);
-    return;
-  }
-
-  var result = [];
-  var remaining = entries.length;
-  this.startBatchUpdates();
-
-  var onOneItem = function(index, value) {
-    result[index] = value;
-    remaining--;
-    if (remaining === 0) {
-      this.endBatchUpdates();
-      if (callback) callback(result);
-    }
-  };
-
-  for (var index = 0; index < entries.length; index++) {
-    result.push(null);
-    this.getOneInternal_(entries[index],
-                         type,
-                         refresh,
-                         onOneItem.bind(this, index));
-  }
-};
-
-/**
- * Fetches the metadata for one Entry. See comments to |get|.
- * If required metadata is already in the cache, does not fetch it again.
- *
- * @param {Entry} entry The entry.
- * @param {string} type Metadata type.
- * @param {function(Object)} callback The metadata is passed to callback.
- *     The callback is called asynchronously.
- */
-MetadataCache.prototype.getOne = function(entry, type, callback) {
-  this.getOneInternal_(entry, type, false, callback);
-};
-
-/**
- * Fetches the metadata for one Entry. This is only for internal use.
- *
- * @param {Entry} entry The entry.
- * @param {string} type Metadata type.
- * @param {boolean} refresh True to get the latest value and refresh the cache,
- *     false to get the value from the cache.
- * @param {function(Object)} callback The metadata is passed to callback.
- *     The callback is called asynchronously.
- * @private
- */
-MetadataCache.prototype.getOneInternal_ =
-    function(entry, type, refresh, callback) {
-  if (type.indexOf('|') !== -1) {
-    var types = type.split('|');
-    var result = {};
-    var typesLeft = types.length;
-
-    var onOneType = function(requestedType, metadata) {
-      result[requestedType] = metadata;
-      typesLeft--;
-      if (typesLeft === 0) callback(result);
-    };
-
-    for (var index = 0; index < types.length; index++) {
-      this.getOneInternal_(entry, types[index], refresh,
-          onOneType.bind(null, types[index]));
-    }
-    return;
-  }
-
-  callback = callback || function() {};
-
-  var entryURL = entry.toURL();
-  if (!(entryURL in this.cache_)) {
-    this.cache_[entryURL] = this.createEmptyItem_();
-    this.totalCount_++;
-  }
-
-  var item = this.cache_[entryURL];
-
-  if (!refresh && type in item.properties) {
-    // Uses cache, if available and not on the 'refresh' mode.
-    setTimeout(callback.bind(null, item.properties[type]), 0);
-    return;
-  }
-
-  this.startBatchUpdates();
-  var providers = this.providers_.slice();
-  var currentProvider;
-  var self = this;
-
-  var queryProvider = function() {
-    var id = currentProvider.getId();
-
-    // If on 'refresh'-mode, replaces the callback array. The previous
-    // array may be remaining in the closure captured by previous tasks.
-    if (refresh)
-      item[id].callbacks = [];
-    var fetchedCallbacks = item[id].callbacks;
-
-    var onFetched = function() {
-      if (type in item.properties) {
-        self.endBatchUpdates();
-        // Got properties from provider.
-        callback(item.properties[type]);
-      } else {
-        tryNextProvider();
-      }
-    };
-
-    var onProviderProperties = function(properties) {
-      var callbacks = fetchedCallbacks.splice(0);
-      item.time = new Date();
-      self.mergeProperties_(entry, properties);
-
-      for (var index = 0; index < callbacks.length; index++) {
-        callbacks[index]();
-      }
-    };
-
-    fetchedCallbacks.push(onFetched);
-
-    // Querying now.
-    if (fetchedCallbacks.length === 1)
-      currentProvider.fetch(entry, type, onProviderProperties);
-  };
-
-  var tryNextProvider = function() {
-    if (providers.length === 0) {
-      self.endBatchUpdates();
-      setTimeout(callback.bind(null, item.properties[type] || null), 0);
-      return;
-    }
-
-    currentProvider = providers.shift();
-    if (currentProvider.supportsEntry(entry) &&
-        currentProvider.providesType(type)) {
-      queryProvider();
-    } else {
-      tryNextProvider();
-    }
-  };
-
-  tryNextProvider();
-};
-
-/**
- * Returns the cached metadata value, or |null| if not present.
- * @param {Entry} entry Entry.
- * @param {string} type The metadata type.
- * @return {Object} The metadata or null.
- */
-MetadataCache.prototype.getCached = function(entry, type) {
-  // Entry.cachedUrl may be set in DirectoryContents.onNewEntries_().
-  // See the comment there for detail.
-  var entryURL = entry.cachedUrl || entry.toURL();
-  var cache = this.cache_[entryURL];
-  return cache ? (cache.properties[type] || null) : null;
-};
-
-/**
- * Puts the metadata into cache
- * @param {Entry|Array.<Entry>} entries The list of entries. May be just a
- *     single entry.
- * @param {string} type The metadata type.
- * @param {Array.<Object>} values List of corresponding metadata values.
- */
-MetadataCache.prototype.set = function(entries, type, values) {
-  if (!(entries instanceof Array)) {
-    entries = [entries];
-    values = [values];
-  }
-
-  this.startBatchUpdates();
-  for (var index = 0; index < entries.length; index++) {
-    var entryURL = entries[index].toURL();
-    if (!(entryURL in this.cache_)) {
-      this.cache_[entryURL] = this.createEmptyItem_();
-      this.totalCount_++;
-    }
-    this.cache_[entryURL].properties[type] = values[index];
-    this.notifyObservers_(entries[index], type);
-  }
-  this.endBatchUpdates();
-};
-
-/**
- * Clears the cached metadata values.
- * @param {Entry|Array.<Entry>} entries The list of entries. May be just a
- *     single entry.
- * @param {string} type The metadata types or * for any type.
- */
-MetadataCache.prototype.clear = function(entries, type) {
-  if (!(entries instanceof Array))
-    entries = [entries];
-
-  this.clearByUrl(
-      entries.map(function(entry) { return entry.toURL(); }),
-      type);
-};
-
-/**
- * Clears the cached metadata values. This method takes an URL since some items
- * may be already removed and can't be fetches their entry.
- *
- * @param {Array.<string>} urls The list of URLs.
- * @param {string} type The metadata types or * for any type.
- */
-MetadataCache.prototype.clearByUrl = function(urls, type) {
-  var types = type.split('|');
-
-  for (var index = 0; index < urls.length; index++) {
-    var entryURL = urls[index];
-    if (entryURL in this.cache_) {
-      if (type === '*') {
-        this.cache_[entryURL].properties = {};
-      } else {
-        for (var j = 0; j < types.length; j++) {
-          var type = types[j];
-          delete this.cache_[entryURL].properties[type];
-        }
-      }
-    }
-  }
-};
-
-/**
- * Clears the cached metadata values recursively.
- * @param {Entry} entry An entry to be cleared recursively from cache.
- * @param {string} type The metadata types or * for any type.
- */
-MetadataCache.prototype.clearRecursively = function(entry, type) {
-  var types = type.split('|');
-  var keys = Object.keys(this.cache_);
-  var entryURL = entry.toURL();
-
-  for (var index = 0; index < keys.length; index++) {
-    var cachedEntryURL = keys[index];
-    if (cachedEntryURL.substring(0, entryURL.length) === entryURL) {
-      if (type === '*') {
-        this.cache_[cachedEntryURL].properties = {};
-      } else {
-        for (var j = 0; j < types.length; j++) {
-          var type = types[j];
-          delete this.cache_[cachedEntryURL].properties[type];
-        }
-      }
-    }
-  }
-};
-
-/**
- * Adds an observer, which will be notified when metadata changes.
- * @param {Entry} entry The root entry to look at.
- * @param {number} relation This defines, which items will trigger the observer.
- *     See comments to |MetadataCache.EXACT| and others.
- * @param {string} type The metadata type.
- * @param {function(Array.<Entry>, Object.<string, Object>)} observer Map of
- *     entries and corresponding metadata values are passed to this callback.
- * @return {number} The observer id, which can be used to remove it.
- */
-MetadataCache.prototype.addObserver = function(
-    entry, relation, type, observer) {
-  var entryURL = entry.toURL();
-
-  // Escape following regexp special characters:
-  // \^$.*+?|&{}[]()<>
-  var escapedEntryURL = entryURL.replace(
-      /([\\\^\$\.\*\+\?\|\&\{\}\[\]\(\)\<\>])/g,
-      '\\$1');
-
-  var re;
-  if (relation === MetadataCache.CHILDREN)
-    re = escapedEntryURL + '(/[^/]*)?';
-  else if (relation === MetadataCache.DESCENDANTS)
-    re = escapedEntryURL + '(/.*)?';
-  else
-    re = escapedEntryURL;
-
-  var id = ++this.observerId_;
-  this.observers_.push({
-    re: new RegExp('^' + re + '$'),
-    type: type,
-    callback: observer,
-    id: id,
-    pending: {}
-  });
-
-  return id;
-};
-
-/**
- * Removes the observer.
- * @param {number} id Observer id.
- * @return {boolean} Whether observer was removed or not.
- */
-MetadataCache.prototype.removeObserver = function(id) {
-  for (var index = 0; index < this.observers_.length; index++) {
-    if (this.observers_[index].id === id) {
-      this.observers_.splice(index, 1);
-      return true;
-    }
-  }
-  return false;
-};
-
-/**
- * Start batch updates.
- */
-MetadataCache.prototype.startBatchUpdates = function() {
-  this.batchCount_++;
-  if (this.batchCount_ === 1)
-    this.lastBatchStart_ = new Date();
-};
-
-/**
- * End batch updates. Notifies observers if all nested updates are finished.
- */
-MetadataCache.prototype.endBatchUpdates = function() {
-  this.batchCount_--;
-  if (this.batchCount_ !== 0) return;
-  if (this.totalCount_ > this.currentEvictionThreshold_())
-    this.evict_();
-  for (var index = 0; index < this.observers_.length; index++) {
-    var observer = this.observers_[index];
-    var entries = [];
-    var properties = {};
-    for (var entryURL in observer.pending) {
-      if (observer.pending.hasOwnProperty(entryURL) &&
-          entryURL in this.cache_) {
-        var entry = observer.pending[entryURL];
-        entries.push(entry);
-        properties[entryURL] =
-            this.cache_[entryURL].properties[observer.type] || null;
-      }
-    }
-    observer.pending = {};
-    if (entries.length > 0) {
-      observer.callback(entries, properties);
-    }
-  }
-};
-
-/**
- * Notifies observers or puts the data to pending list.
- * @param {Entry} entry Changed entry.
- * @param {string} type Metadata type.
- * @private
- */
-MetadataCache.prototype.notifyObservers_ = function(entry, type) {
-  var entryURL = entry.toURL();
-  for (var index = 0; index < this.observers_.length; index++) {
-    var observer = this.observers_[index];
-    if (observer.type === type && observer.re.test(entryURL)) {
-      if (this.batchCount_ === 0) {
-        // Observer expects array of urls and map of properties.
-        var property = {};
-        property[entryURL] = this.cache_[entryURL].properties[type] || null;
-        observer.callback(
-            [entry], property);
-      } else {
-        observer.pending[entryURL] = entry;
-      }
-    }
-  }
-};
-
-/**
- * Removes the oldest items from the cache.
- * This method never removes the items from last batch.
- * @private
- */
-MetadataCache.prototype.evict_ = function() {
-  var toRemove = [];
-
-  // We leave only a half of items, so we will not call evict_ soon again.
-  var desiredCount = this.currentEvictionThreshold_();
-  var removeCount = this.totalCount_ - desiredCount;
-  for (var url in this.cache_) {
-    if (this.cache_.hasOwnProperty(url) &&
-        this.cache_[url].time < this.lastBatchStart_) {
-      toRemove.push(url);
-    }
-  }
-
-  toRemove.sort(function(a, b) {
-    var aTime = this.cache_[a].time;
-    var bTime = this.cache_[b].time;
-    return aTime < bTime ? -1 : aTime > bTime ? 1 : 0;
-  }.bind(this));
-
-  removeCount = Math.min(removeCount, toRemove.length);
-  this.totalCount_ -= removeCount;
-  for (var index = 0; index < removeCount; index++) {
-    delete this.cache_[toRemove[index]];
-  }
-};
-
-/**
- * @return {Object} Empty cache item.
- * @private
- */
-MetadataCache.prototype.createEmptyItem_ = function() {
-  var item = {properties: {}};
-  for (var index = 0; index < this.providers_.length; index++) {
-    item[this.providers_[index].getId()] = {callbacks: []};
-  }
-  return item;
-};
-
-/**
- * Caches all the properties from data to cache entry for the entry.
- * @param {Entry} entry The file entry.
- * @param {Object} data The properties.
- * @private
- */
-MetadataCache.prototype.mergeProperties_ = function(entry, data) {
-  if (data === null) return;
-  var entryURL = entry.toURL();
-  if (!(entryURL in this.cache_)) {
-    this.cache_[entryURL] = this.createEmptyItem_();
-    this.totalCount_++;
-  }
-  var properties = this.cache_[entryURL].properties;
-  for (var type in data) {
-    if (data.hasOwnProperty(type)) {
-      properties[type] = data[type];
-      this.notifyObservers_(entry, type);
-    }
-  }
-};
-
-/**
- * Base class for metadata providers.
- * @constructor
- */
-function MetadataProvider() {
-}
-
-/**
- * @param {Entry} entry The entry.
- * @return {boolean} Whether this provider supports the entry.
- */
-MetadataProvider.prototype.supportsEntry = function(entry) { return false; };
-
-/**
- * @param {string} type The metadata type.
- * @return {boolean} Whether this provider provides this metadata.
- */
-MetadataProvider.prototype.providesType = function(type) { return false; };
-
-/**
- * @return {string} Unique provider id.
- */
-MetadataProvider.prototype.getId = function() { return ''; };
-
-/**
- * @return {boolean} Whether provider is ready.
- */
-MetadataProvider.prototype.isInitialized = function() { return true; };
-
-/**
- * Fetches the metadata. It's suggested to return all the metadata this provider
- * can fetch at once.
- * @param {Entry} entry File entry.
- * @param {string} type Requested metadata type.
- * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value. This callback must be called asynchronously.
- */
-MetadataProvider.prototype.fetch = function(entry, type, callback) {
-  throw new Error('Default metadata provider cannot fetch.');
-};
-
-
-/**
- * Provider of filesystem metadata.
- * This provider returns the following objects:
- * filesystem: { size, modificationTime }
- * @constructor
- * @extends {MetadataProvider}
- */
-function FilesystemProvider() {
-  MetadataProvider.call(this);
-}
-
-FilesystemProvider.prototype = {
-  __proto__: MetadataProvider.prototype
-};
-
-/**
- * @param {Entry} entry The entry.
- * @return {boolean} Whether this provider supports the entry.
- */
-FilesystemProvider.prototype.supportsEntry = function(entry) {
-  return true;
-};
-
-/**
- * @param {string} type The metadata type.
- * @return {boolean} Whether this provider provides this metadata.
- */
-FilesystemProvider.prototype.providesType = function(type) {
-  return type === 'filesystem';
-};
-
-/**
- * @return {string} Unique provider id.
- */
-FilesystemProvider.prototype.getId = function() { return 'filesystem'; };
-
-/**
- * Fetches the metadata.
- * @param {Entry} entry File entry.
- * @param {string} type Requested metadata type.
- * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value. This callback is called asynchronously.
- */
-FilesystemProvider.prototype.fetch = function(
-    entry, type, callback) {
-  function onError(error) {
-    callback(null);
-  }
-
-  function onMetadata(entry, metadata) {
-    callback({
-      filesystem: {
-        size: (entry.isFile ? (metadata.size || 0) : -1),
-        modificationTime: metadata.modificationTime
-      }
-    });
-  }
-
-  entry.getMetadata(onMetadata.bind(null, entry), onError);
-};
-
-/**
- * Provider of metadata for entries on the external file system backend.
- * This provider returns the following objects:
- *     external: { pinned, hosted, present, customIconUrl, etc. }
- *     thumbnail: { url, transform }
- * @param {VolumeManagerWrapper} volumeManager Volume manager instance.
- * @constructor
- * @extends {MetadataProvider}
- */
-function ExternalProvider(volumeManager) {
-  MetadataProvider.call(this);
-
-  /**
-   * @type {VolumeManagerWrapper}
-   * @private
-   */
-  this.volumeManager_ = volumeManager;
-
-  // We batch metadata fetches into single API call.
-  this.entries_ = [];
-  this.callbacks_ = [];
-  this.scheduled_ = false;
-
-  this.callApiBound_ = this.callApi_.bind(this);
-}
-
-ExternalProvider.prototype = {
-  __proto__: MetadataProvider.prototype
-};
-
-/**
- * @param {Entry} entry The entry.
- * @return {boolean} Whether this provider supports the entry.
- */
-ExternalProvider.prototype.supportsEntry = function(entry) {
-  var locationInfo = this.volumeManager_.getLocationInfo(entry);
-  if (!locationInfo)
-    return false;
-  return locationInfo.isDriveBased ||
-      locationInfo.rootType === VolumeManagerCommon.RootType.PROVIDED;
-};
-
-/**
- * @param {string} type The metadata type.
- * @return {boolean} Whether this provider provides this metadata.
- */
-ExternalProvider.prototype.providesType = function(type) {
-  return type === 'external' || type === 'thumbnail' ||
-      type === 'media' || type === 'filesystem';
-};
-
-/**
- * @return {string} Unique provider id.
- */
-ExternalProvider.prototype.getId = function() { return 'external'; };
-
-/**
- * Fetches the metadata.
- * @param {Entry} entry File entry.
- * @param {string} type Requested metadata type.
- * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value. This callback is called asynchronously.
- */
-ExternalProvider.prototype.fetch = function(entry, type, callback) {
-  this.entries_.push(entry);
-  this.callbacks_.push(callback);
-  if (!this.scheduled_) {
-    this.scheduled_ = true;
-    setTimeout(this.callApiBound_, 0);
-  }
-};
-
-/**
- * Schedules the API call.
- * @private
- */
-ExternalProvider.prototype.callApi_ = function() {
-  this.scheduled_ = false;
-
-  var entries = this.entries_;
-  var callbacks = this.callbacks_;
-  this.entries_ = [];
-  this.callbacks_ = [];
-  var self = this;
-
-  // TODO(mtomasz): Move conversion from entry to url to custom bindings.
-  // crbug.com/345527.
-  var entryURLs = util.entriesToURLs(entries);
-  chrome.fileManagerPrivate.getEntryProperties(
-      entryURLs,
-      function(propertiesList) {
-        console.assert(propertiesList.length === callbacks.length);
-        for (var i = 0; i < callbacks.length; i++) {
-          callbacks[i](self.convert_(propertiesList[i], entries[i]));
-        }
-      });
-};
-
-/**
- * Converts API metadata to internal format.
- * @param {Object} data Metadata from API call.
- * @param {Entry} entry File entry.
- * @return {Object} Metadata in internal format.
- * @private
- */
-ExternalProvider.prototype.convert_ = function(data, entry) {
-  var result = {};
-  result.external = {
-    present: data.isPresent,
-    pinned: data.isPinned,
-    hosted: data.isHosted,
-    imageWidth: data.imageWidth,
-    imageHeight: data.imageHeight,
-    imageRotation: data.imageRotation,
-    availableOffline: data.isAvailableOffline,
-    availableWhenMetered: data.isAvailableWhenMetered,
-    customIconUrl: data.customIconUrl || '',
-    contentMimeType: data.contentMimeType || '',
-    sharedWithMe: data.sharedWithMe,
-    shared: data.shared,
-    thumbnailUrl: data.thumbnailUrl  // Thumbnail passed from external server.
-  };
-
-  result.filesystem = {
-    size: (entry.isFile ? (data.fileSize || 0) : -1),
-    modificationTime: new Date(data.lastModifiedTime)
-  };
-
-  if (data.isPresent) {
-    // If the file is present, don't fill the thumbnail here and allow to
-    // generate it by next providers.
-    result.thumbnail = null;
-  } else if ('thumbnailUrl' in data) {
-    result.thumbnail = {
-      url: data.thumbnailUrl,
-      transform: null
-    };
-  } else {
-    // Not present in cache, so do not allow to generate it by next providers.
-    result.thumbnail = {url: '', transform: null};
-  }
-
-  // If present in cache, then allow to fetch media by next providers.
-  result.media = data.isPresent ? null : {};
-
-  return result;
-};
-
-
-/**
- * Provider of content metadata.
- * This provider returns the following objects:
- * thumbnail: { url, transform }
- * media: { artist, album, title, width, height, imageTransform, etc. }
- * fetchedMedia: { same fields here }
- * @constructor
- * @extends {MetadataProvider}
- */
-function ContentProvider() {
-  MetadataProvider.call(this);
-
-  // Pass all URLs to the metadata reader until we have a correct filter.
-  this.urlFilter_ = /.*/;
-
-  var dispatcher = new SharedWorker(ContentProvider.WORKER_SCRIPT).port;
-  dispatcher.onmessage = this.onMessage_.bind(this);
-  dispatcher.postMessage({verb: 'init'});
-  dispatcher.start();
-  this.dispatcher_ = dispatcher;
-
-  // Initialization is not complete until the Worker sends back the
-  // 'initialized' message.  See below.
-  this.initialized_ = false;
-
-  // Map from Entry.toURL() to callback.
-  // Note that simultaneous requests for same url are handled in MetadataCache.
-  this.callbacks_ = {};
-}
-
-/**
- * Path of a worker script.
- * @type {string}
- * @const
- */
-ContentProvider.WORKER_SCRIPT =
-    'chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/' +
-    'foreground/js/metadata/metadata_dispatcher.js';
-
-ContentProvider.prototype = {
-  __proto__: MetadataProvider.prototype
-};
-
-/**
- * @param {Entry} entry The entry.
- * @return {boolean} Whether this provider supports the entry.
- */
-ContentProvider.prototype.supportsEntry = function(entry) {
-  return !!entry.toURL().match(this.urlFilter_);
-};
-
-/**
- * @param {string} type The metadata type.
- * @return {boolean} Whether this provider provides this metadata.
- */
-ContentProvider.prototype.providesType = function(type) {
-  return type === 'thumbnail' || type === 'fetchedMedia' || type === 'media';
-};
-
-/**
- * @return {string} Unique provider id.
- */
-ContentProvider.prototype.getId = function() { return 'content'; };
-
-/**
- * Fetches the metadata.
- * @param {Entry} entry File entry.
- * @param {string} type Requested metadata type.
- * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value. This callback is called asynchronously.
- */
-ContentProvider.prototype.fetch = function(entry, type, callback) {
-  if (entry.isDirectory) {
-    setTimeout(callback.bind(null, {}), 0);
-    return;
-  }
-  var entryURL = entry.toURL();
-  this.callbacks_[entryURL] = callback;
-  this.dispatcher_.postMessage({verb: 'request', arguments: [entryURL]});
-};
-
-/**
- * Dispatch a message from a metadata reader to the appropriate on* method.
- * @param {Object} event The event.
- * @private
- */
-ContentProvider.prototype.onMessage_ = function(event) {
-  var data = event.data;
-
-  var methodName =
-      'on' + data.verb.substr(0, 1).toUpperCase() + data.verb.substr(1) + '_';
-
-  if (!(methodName in this)) {
-    console.error('Unknown message from metadata reader: ' + data.verb, data);
-    return;
-  }
-
-  this[methodName].apply(this, data.arguments);
-};
-
-/**
- * @return {boolean} Whether provider is ready.
- */
-ContentProvider.prototype.isInitialized = function() {
-  return this.initialized_;
-};
-
-/**
- * Handles the 'initialized' message from the metadata reader Worker.
- * @param {Object} regexp Regexp of supported urls.
- * @private
- */
-ContentProvider.prototype.onInitialized_ = function(regexp) {
-  this.urlFilter_ = regexp;
-
-  // Tests can monitor for this state with
-  // ExtensionTestMessageListener listener("worker-initialized");
-  // ASSERT_TRUE(listener.WaitUntilSatisfied());
-  // Automated tests need to wait for this, otherwise we crash in
-  // browser_test cleanup because the worker process still has
-  // URL requests in-flight.
-  util.testSendMessage('worker-initialized');
-  this.initialized_ = true;
-};
-
-/**
- * Converts content metadata from parsers to the internal format.
- * @param {Object} metadata The content metadata.
- * @param {Object=} opt_result The internal metadata object ot put result in.
- * @return {Object!} Converted metadata.
- */
-ContentProvider.ConvertContentMetadata = function(metadata, opt_result) {
-  var result = opt_result || {};
-
-  if ('thumbnailURL' in metadata) {
-    metadata.thumbnailTransform = metadata.thumbnailTransform || null;
-    result.thumbnail = {
-      url: metadata.thumbnailURL,
-      transform: metadata.thumbnailTransform
-    };
-  }
-
-  for (var key in metadata) {
-    if (metadata.hasOwnProperty(key)) {
-      if (!result.media)
-        result.media = {};
-      result.media[key] = metadata[key];
-    }
-  }
-
-  if (result.media)
-    result.fetchedMedia = result.media;
-
-  return result;
-};
-
-/**
- * Handles the 'result' message from the worker.
- * @param {string} url File url.
- * @param {Object} metadata The metadata.
- * @private
- */
-ContentProvider.prototype.onResult_ = function(url, metadata) {
-  var callback = this.callbacks_[url];
-  delete this.callbacks_[url];
-  callback(ContentProvider.ConvertContentMetadata(metadata));
-};
-
-/**
- * Handles the 'error' message from the worker.
- * @param {string} url File entry.
- * @param {string} step Step failed.
- * @param {string} error Error description.
- * @param {Object?} metadata The metadata, if available.
- * @private
- */
-ContentProvider.prototype.onError_ = function(url, step, error, metadata) {
-  if (MetadataCache.log)  // Avoid log spam by default.
-    console.warn('metadata: ' + url + ': ' + step + ': ' + error);
-  metadata = metadata || {};
-  // Prevent asking for thumbnail again.
-  metadata.thumbnailURL = '';
-  this.onResult_(url, metadata);
-};
-
-/**
- * Handles the 'log' message from the worker.
- * @param {Array.<*>} arglist Log arguments.
- * @private
- */
-ContentProvider.prototype.onLog_ = function(arglist) {
-  if (MetadataCache.log)  // Avoid log spam by default.
-    console.log.apply(console, ['metadata:'].concat(arglist));
-};