Extract ContentScanner from DirectoryContent.

chrome/browser/resources/file_manager/js/directory_contents.js

Index: chrome/browser/resources/file_manager/js/directory_contents.js
diff --git a/chrome/browser/resources/file_manager/js/directory_contents.js b/chrome/browser/resources/file_manager/js/directory_contents.js
index be916c1e51fc38a9e89076d78b8fefe0b1cf7b94..fece6f207fd0335fe38c46a933683be436821ae8 100644
--- a/chrome/browser/resources/file_manager/js/directory_contents.js
+++ b/chrome/browser/resources/file_manager/js/directory_contents.js
@@ -5,6 +5,341 @@
 'use strict';
 
 /**
+ * Scanner of the entries.
+ * @constructor
+ */
+function ContentScanner() {
+  this.cancelled_ = false;
+}
+
+/**
+ * Starts to scan the entries. For example, starts to read the entries in a
+ * directory, or starts to search with some query on a file system.
+ * Derived classes must override this method.
+ *
+ * @param {function(Array.<Entry>)} entriesCallback Called when some chunk of
+ *     entries are read. This can be called a couple of times until the
+ *     completion.
+ * @param {function()} successCallback Called when the scan is completed
+ *     successfully.
+ * @param {function(FileError)} errorCallback Called an error occurs.
+ */
+ContentScanner.prototype.scan = function(
+    entriesCallback, successCallback, errorCallback) {
+};
+
+/**
+ * Request cancelling of the running scan. When the cancelling is done,
+ * an error will be reported from errorCallback passed to scan().
+ */
+ContentScanner.prototype.cancel = function() {
+  this.cancelled_ = true;
+};
+
+/**
+ * Scanner of the entries in a directory.
+ * @param {DirectoryEntry} entry The directory to be read.
+ * @constructor
+ * @extends {ContentScanner}
+ */
+function DirectoryContentScanner(entry) {
+  ContentScanner.call(this);
+  this.entry_ = entry;
+}
+
+/**
+ * Extends ContentScanner.
+ */
+DirectoryContentScanner.prototype.__proto__ = ContentScanner.prototype;
+
+/**
+ * Starts to read the entries in the directory.
+ * @param {function(Array.<Entry>)} entriesCallback Called when some chunk of
+ *     entries are read. This can be called a couple of times until the
+ *     completion.
+ * @param {function()} successCallback Called when the scan is completed
+ *     successfully.
+ * @param {function(FileError)} errorCallback Called an error occurs.
+ * @override
+ */
+DirectoryContentScanner.prototype.scan = function(
+    entriesCallback, successCallback, errorCallback) {
+  if (!this.entry_ || this.entry_ === DirectoryModel.fakeDriveEntry_) {
+    // If entry is not specified or a fake, we cannot read it.
+    errorCallback(util.createFileError(FileError.INVALID_MODIFICATION_ERR));
+    return;
+  }
+
+  metrics.startInterval('DirectoryScan');
+  var reader = this.entry_.createReader();
+  var readEntries = function() {
+    reader.readEntries(
+        function(entries) {
+          if (this.cancelled_) {
+            errorCallback(util.createFileError(FileError.ABORT_ERR));
+            return;
+          }
+
+          if (entries.length === 0) {
+            // All entries are read.
+            metrics.recordInterval('DirectoryScan');
+            successCallback();
+            return;
+          }
+
+          entriesCallback(entries);
+          readEntries();
+        }.bind(this),
+        errorCallback);
+  }.bind(this);
+  readEntries();
+};
+
+/**
+ * Scanner of the entries for the search results on Drive File System.
+ * @param {string} query The query string.
+ * @constructor
+ * @extends {ContentScanner}
+ */
+function DriveSearchContentScanner(query) {
+  ContentScanner.call(this);
+  this.query_ = query;
+}
+
+/**
+ * Extends ContentScanner.
+ */
+DriveSearchContentScanner.prototype.__proto__ = ContentScanner.prototype;
+
+/**
+ * Delay in milliseconds to be used for drive search scan, in order to reduce
+ * the number of server requests while user is typing the query.
+ * @type {number}
+ * @private
+ * @const
+ */
+DriveSearchContentScanner.SCAN_DELAY_ = 200;
+
+/**
+ * Maximum number of results which is shown on the search.
+ * @type {number}
+ * @private
+ * @const
+ */
+DriveSearchContentScanner.MAX_RESULTS_ = 100;
+
+/**
+ * Starts to search on Drive File System.
+ * @param {function(Array.<Entry>)} entriesCallback Called when some chunk of
+ *     entries are read. This can be called a couple of times until the
+ *     completion.
+ * @param {function()} successCallback Called when the scan is completed
+ *     successfully.
+ * @param {function(FileError)} errorCallback Called an error occurs.
+ * @override
+ */
+DriveSearchContentScanner.prototype.scan = function(
+    entriesCallback, successCallback, errorCallback) {
+  var numReadEntries = 0;
+  var readEntries = function(nextFeed) {
+    chrome.fileBrowserPrivate.searchDrive(
+        {query: this.query_, nextFeed: nextFeed},
+        function(entries, nextFeed) {
+          if (this.cancelled_) {
+            errorCallback(util.createFileError(FileError.ABORT_ERR));
+            return;
+          }
+
+          // TODO(tbarzic): Improve error handling.
+          if (!entries) {
+            console.error('Drive search encountered an error.');
+            errorCallback(util.createFileError(
+                FileError.INVALID_MODIFICATION_ERR));
+            return;
+          }
+
+          var numRemainingEntries =
+              DriveSearchContentScanner.MAX_RESULTS_ - numReadEntries;
+          if (entries.length >= numRemainingEntries) {
+            // The limit is hit, so quit the scan here.
+            entries = entries.slice(0, numRemainingEntries);
+            nextFeed = '';
+          }
+
+          numReadEntries += entries.length;
+          if (entries.length > 0)
+            entriesCallback(entries);
+
+          if (nextFeed === '')
+            successCallback();
+          else
+            readEntries(nextFeed);
+        }.bind(this));
+  }.bind(this);
+
+  // Let's give another search a chance to cancel us before we begin.
+  setTimeout(
+      function() {
+        // Check cancelled state before read the entries.
+        if (this.cancelled_) {
+          errorCallback(util.createFileError(FileError.ABORT_ERR));
+          return;
+        }
+        readEntries('');
+      }.bind(this),
+      DriveSearchContentScanner.SCAN_DELAY_);
+};
+
+/**
+ * Scanner of the entries of the file name search on the directory tree, whose
+ * root is entry.
+ * @param {DirectoryEntry} entry The root of the search target directory tree.
+ * @param {string} query The query of the search.
+ * @constructor
+ * @extends {ContentScanner}
+ */
+function LocalSearchContentScanner(entry, query) {
+  ContentScanner.call(this);
+  this.entry_ = entry;
+  this.query_ = query.toLowerCase();
+}
+
+/**
+ * Extedns ContentScanner.
+ */
+LocalSearchContentScanner.prototype.__proto__ = ContentScanner.prototype;
+
+/**
+ * Starts the file name search.
+ * @param {function(Array.<Entry>)} entriesCallback Called when some chunk of
+ *     entries are read. This can be called a couple of times until the
+ *     completion.
+ * @param {function()} successCallback Called when the scan is completed
+ *     successfully.
+ * @param {function(FileError)} errorCallback Called an error occurs.
+ * @override
+ */
+LocalSearchContentScanner.prototype.scan = function(
+    entriesCallback, successCallback, errorCallback) {
+  var numRunningTasks = 0;
+  var error = null;
+  var maybeRunCallback = function() {
+    if (numRunningTasks === 0) {
+      if (this.cancelled_)
+        errorCallback(util.createFileError(FileError.ABORT_ERR));
+      else if (error)
+        errorCallback(error);
+      else
+        successCallback();
+    }
+  }.bind(this);
+
+  var processEntry = function(entry) {
+    numRunningTasks++;
+    var onError = function(fileError) {
+      if (!error)
+        error = fileError;
+      numRunningTasks--;
+      maybeRunCallback();
+    };
+
+    var onSuccess = function(entries) {
+      if (this.cancelled_ || error || entries.length === 0) {
+        numRunningTasks--;
+        maybeRunCallback();
+        return;
+      }
+
+      // Filters by the query, and if found, run entriesCallback.
+      var foundEntries = entries.filter(function(entry) {
+        return entry.name.toLowerCase().indexOf(this.query_) >= 0;
+      }.bind(this));
+      if (foundEntries.length > 0)
+        entriesCallback(foundEntries);
+
+      // Start to process sub directories.
+      for (var i = 0; i < entries.length; i++) {
+        if (entries[i].isDirectory)
+          processEntry(entries[i]);
+      }
+
+      // Read remaining entries.
+      reader.readEntries(onSuccess, onError);
+    }.bind(this);
+
+    var reader = entry.createReader();
+    reader.readEntries(onSuccess, onError);
+  }.bind(this);
+
+  processEntry(this.entry_);
+};
+
+/**
+ * Scanner of the entries for the metadata seaerch on Drive File System.
+ * @param {string} query The query of the search.
+ * @param {DriveMetadataSearchContentScanner.SearchType} searchType The option
+ *     of the search.
+ * @constructor
+ * @extends {ContentScanner}
+ */
+function DriveMetadataSearchContentScanner(query, searchType) {
+  ContentScanner.call(this);
+  this.query_ = query;
+  this.searchType_ = searchType;
+}
+
+/**
+ * Extends ContentScanner.
+ */
+DriveMetadataSearchContentScanner.prototype.__proto__ =
+    ContentScanner.prototype;
+
+/**
+ * The search types on the Drive File System.
+ * @enum {string}
+ */
+DriveMetadataSearchContentScanner.SearchType = Object.freeze({
+  SEARCH_ALL: 'ALL',
+  SEARCH_SHARED_WITH_ME: 'SHARED_WITH_ME',
+  SEARCH_RECENT_FILES: 'EXCLUDE_DIRECTORIES',
+  SEARCH_OFFLINE: 'OFFLINE'
+});
+
+/**
+ * Starts to metadata-search on Drive File System.
+ * @param {function(Array.<Entry>)} entriesCallback Called when some chunk of
+ *     entries are read. This can be called a couple of times until the
+ *     completion.
+ * @param {function()} successCallback Called when the scan is completed
+ *     successfully.
+ * @param {function(FileError)} errorCallback Called an error occurs.
+ * @override
+ */
+DriveMetadataSearchContentScanner.prototype.scan = function(
+    entriesCallback, successCallback, errorCallback) {
+  chrome.fileBrowserPrivate.searchDriveMetadata(
+      {query: this.query_, types: this.searchType_, maxResults: 500},
+      function(results) {
+        if (this.cancelled_) {
+          errorCallback(util.createFileError(FileError.ABORT_ERR));
+          return;
+        }
+
+        if (!results) {
+          console.error('Drive search encountered an error.');
+          errorCallback(util.createFileError(
+              FileError.INVALID_MODIFICATION_ERR));
+          return;
+        }
+
+        var entries = results.map(function(result) { return result.entry; });
+        if (entries.length > 0)
+          entriesCallback(entries);
+        successCallback();
+      }.bind(this));
+};
+
+/**
  * This class manages filters and determines a file should be shown or not.
  * When filters are changed, a 'changed' event is fired.
  *
@@ -19,6 +354,7 @@ function FileFilter(metadataCache, showHidden) {
    * @private
    */
   this.metadataCache_ = metadataCache;
+
   /**
    * @type Object.<string, Function>
    * @private
@@ -102,6 +438,7 @@ function FileListContext(fileFilter, metadataCache) {
    * @type {cr.ui.ArrayDataModel}
    */
   this.fileList = new cr.ui.ArrayDataModel([]);
+
   /**
    * @type {MetadataCache}
    */
@@ -125,11 +462,8 @@ function FileListContext(fileFilter, metadataCache) {
 function DirectoryContents(context) {
   this.context_ = context;
   this.fileList_ = context.fileList;
-  this.scanCompletedCallback_ = null;
-  this.scanFailedCallback_ = null;
+  this.prefetchMetadataQueue_ = new AsyncUtil.Queue();
   this.scanCancelled_ = false;
-  this.allChunksFetched_ = false;
-  this.pendingMetadataRequests_ = 0;
   this.fileList_.prepareSort = this.prepareSort_.bind(this);
 }
 
@@ -173,8 +507,7 @@ DirectoryContents.prototype.replaceContextFileList = function() {
  * @return {boolean} If the scan is active.
  */
 DirectoryContents.prototype.isScanning = function() {
-  return !this.scanCancelled_ &&
-         (!this.allChunksFetched_ || this.pendingMetadataRequests_ > 0);
+  return this.scanner_ || this.prefetchMetadataQueue_.isRunning();
 };
 
 /**
@@ -208,40 +541,84 @@ DirectoryContents.prototype.scan = function() {
 };
 
 /**
- * Read next chunk of results from DirectoryReader.
- * @protected
- */
-DirectoryContents.prototype.readNextChunk = function() {
-  throw 'Not implemented.';
-};
-
-/**
- * Cancel the running scan.
+ * Cancels the running scan.
  */
 DirectoryContents.prototype.cancelScan = function() {
   if (this.scanCancelled_)
     return;
   this.scanCancelled_ = true;
+  if (this.scanner_)
+    this.scanner_.cancel();
+
+  this.prefetchMetadataQueue_.cancel();
   cr.dispatchSimpleEvent(this, 'scan-cancelled');
 };
 
+/**
+ * Called when the scanning by scanner_ is done.
+ * @protected
+ */
+DirectoryContents.prototype.onScanCompleted = function() {
+  this.scanner_ = null;
+  if (this.scanCancelled_)
+    return;
+
+  this.prefetchMetadataQueue_.run(function(callback) {
+    cr.dispatchSimpleEvent(this, 'scan-completed');
+    if (!this.isSearch() &&
+        this.getDirectoryEntry().fullPath === RootDirectory.DOWNLOADS)
+      metrics.recordMediumCount('DownloadsCount', this.fileList_.length);
+    callback();
+  }.bind(this));
+};
 
 /**
  * Called in case scan has failed. Should send the event.
  * @protected
  */
-DirectoryContents.prototype.onError = function() {
-  cr.dispatchSimpleEvent(this, 'scan-failed');
+DirectoryContents.prototype.onScanError = function() {
+  this.scanner_ = null;
+  if (this.scanCancelled_)
+    return;
+
+  this.prefetchMetadataQueue_.run(function(callback) {
+    cr.dispatchSimpleEvent(this, 'scan-failed');
+    callback();
+  }.bind(this));
 };
 
 /**
- * Called in case scan has completed succesfully. Should send the event.
+ * Called when some chunk of entries are read by scanner.
+ * @param {Array.<Entry>} entries The list of the scanned entries.
  * @protected
  */
-DirectoryContents.prototype.lastChunkReceived = function() {
-  this.allChunksFetched_ = true;
-  if (!this.scanCancelled_ && this.pendingMetadataRequests_ === 0)
-    cr.dispatchSimpleEvent(this, 'scan-completed');
+DirectoryContents.prototype.onNewEntries = function(entries) {
+  if (this.scanCancelled_)
+    return;
+
+  var entriesFiltered = [].filter.call(
+      entries, this.context_.fileFilter.filter.bind(this.context_.fileFilter));
+
+  // Because the prefetchMetadata can be slow, throttling by splitting entries
+  // into smaller chunks to reduce UI latency.
+  // TODO(hidehiko,mtomasz): This should be handled in MetadataCache.
+  var MAX_CHUNK_SIZE = 50;
+  for (var i = 0; i < entriesFiltered.length; i += MAX_CHUNK_SIZE) {
+    var chunk = entriesFiltered.slice(i, i + MAX_CHUNK_SIZE);
+    this.prefetchMetadataQueue_.run(function(chunk, callback) {
+      this.prefetchMetadata(chunk, function() {
+        if (this.scanCancelled_) {
+          // Do nothing if the scanning is cancelled.
+          callback();
+          return;
+        }
+
+        this.fileList_.push.apply(this.fileList_, chunk);
+        cr.dispatchSimpleEvent(this, 'scan-updated');
+        callback();
+      }.bind(this));
+    }.bind(this, chunk));
+  }
 };
 
 /**
@@ -275,36 +652,6 @@ DirectoryContents.prototype.reloadMetadata = function(entries, callback) {
 };
 
 /**
- * @protected
- * @param {Array.<Entry>} entries File list.
- */
-DirectoryContents.prototype.onNewEntries = function(entries) {
-  if (this.scanCancelled_)
-    return;
-
-  var entriesFiltered = [].filter.call(
-      entries, this.context_.fileFilter.filter.bind(this.context_.fileFilter));
-
-  var onPrefetched = function() {
-    this.pendingMetadataRequests_--;
-    if (this.scanCancelled_)
-      return;
-    this.fileList_.push.apply(this.fileList_, entriesFiltered);
-
-    if (this.pendingMetadataRequests_ === 0 && this.allChunksFetched_)
-      cr.dispatchSimpleEvent(this, 'scan-completed');
-    else
-      cr.dispatchSimpleEvent(this, 'scan-updated');
-
-    if (!this.allChunksFetched_)
-      this.readNextChunk();
-  };
-
-  this.pendingMetadataRequests_++;
-  this.prefetchMetadata(entriesFiltered, onPrefetched.bind(this));
-};
-
-/**
  * @param {string} name Directory name.
  * @param {function(DirectoryEntry)} successCallback Called on success.
  * @param {function(FileError)} errorCallback On error.
@@ -357,49 +704,12 @@ DirectoryContentsBasic.prototype.getLastNonSearchDirectoryEntry = function() {
  * Start directory scan.
  */
 DirectoryContentsBasic.prototype.scan = function() {
-  if (!this.entry_ || this.entry_ === DirectoryModel.fakeDriveEntry_) {
-    this.lastChunkReceived();
-    return;
-  }
-
-  metrics.startInterval('DirectoryScan');
-  this.reader_ = this.entry_.createReader();
-  this.readNextChunk();
-};
-
-/**
- * Read next chunk of results from DirectoryReader.
- * @protected
- */
-DirectoryContentsBasic.prototype.readNextChunk = function() {
-  this.reader_.readEntries(this.onChunkComplete_.bind(this),
-                           this.onError.bind(this));
-};
-
-/**
- * @param {Array.<Entry>} entries File list.
- * @private
- */
-DirectoryContentsBasic.prototype.onChunkComplete_ = function(entries) {
-  if (this.scanCancelled_)
-    return;
-
-  if (entries.length == 0) {
-    this.lastChunkReceived();
-    this.recordMetrics_();
-    return;
-  }
-
-  this.onNewEntries(entries);
-};
-
-/**
- * @private
- */
-DirectoryContentsBasic.prototype.recordMetrics_ = function() {
-  metrics.recordInterval('DirectoryScan');
-  if (this.entry_.fullPath === RootDirectory.DOWNLOADS)
-    metrics.recordMediumCount('DownloadsCount', this.fileList_.length);
+  // TODO(hidehiko,mtomasz): this scan method must be called at most once.
+  // Remove such a limitation.
+  this.scanner_ = new DirectoryContentScanner(this.entry_);
+  this.scanner_.scan(this.onNewEntries.bind(this),
+                     this.onScanCompleted.bind(this),
+                     this.onScanError.bind(this));
 };
 
 /**
@@ -409,6 +719,8 @@ DirectoryContentsBasic.prototype.recordMetrics_ = function() {
  */
 DirectoryContentsBasic.prototype.createDirectory = function(
     name, successCallback, errorCallback) {
+  // TODO(hidehiko): createDirectory should not be the part of
+  // DirectoryContent.
   if (!this.entry_) {
     errorCallback(util.createFileError(FileError.INVALID_MODIFICATION_ERR));
     return;
@@ -425,24 +737,6 @@ DirectoryContentsBasic.prototype.createDirectory = function(
 };
 
 /**
- * Delay to be used for drive search scan.
- * The goal is to reduce the number of server requests when user is typing the
- * query.
- *
- * @type {number}
- * @const
- */
-DirectoryContentsDriveSearch.SCAN_DELAY = 200;
-
-/**
- * Maximum number of results which is shown on the search.
- *
- * @type {number}
- * @const
- */
-DirectoryContentsDriveSearch.MAX_RESULTS = 100;
-
-/**
  * @param {FileListContext} context File list context.
  * @param {DirectoryEntry} dirEntry Current directory.
  * @param {DirectoryEntry} previousDirEntry DirectoryEntry that was current
@@ -459,9 +753,6 @@ function DirectoryContentsDriveSearch(context,
   this.directoryEntry_ = dirEntry;
   this.previousDirectoryEntry_ = previousDirEntry;
   this.query_ = query;
-  this.nextFeed_ = '';
-  this.done_ = false;
-  this.fetchedResultsNum_ = 0;
 }
 
 /**
@@ -507,53 +798,12 @@ DirectoryContentsDriveSearch.prototype.getLastNonSearchDirectoryEntry =
  * Start directory scan.
  */
 DirectoryContentsDriveSearch.prototype.scan = function() {
-  // Let's give another search a chance to cancel us before we begin.
-  setTimeout(this.readNextChunk.bind(this),
-             DirectoryContentsDriveSearch.SCAN_DELAY);
-};
-
-/**
- * All the results are read in one chunk, so when we try to read second chunk,
- * it means we're done.
- */
-DirectoryContentsDriveSearch.prototype.readNextChunk = function() {
-  if (this.scanCancelled_)
-    return;
-
-  if (this.done_) {
-    this.lastChunkReceived();
-    return;
-  }
-
-  var searchCallback = (function(entries, nextFeed) {
-    // TODO(tbarzic): Improve error handling.
-    if (!entries) {
-      console.error('Drive search encountered an error.');
-      this.lastChunkReceived();
-      return;
-    }
-    this.nextFeed_ = nextFeed;
-    var remaining =
-        DirectoryContentsDriveSearch.MAX_RESULTS - this.fetchedResultsNum_;
-    if (entries.length >= remaining) {
-      entries = entries.slice(0, remaining);
-      this.nextFeed_ = '';
-    }
-    this.fetchedResultsNum_ += entries.length;
-
-    this.done_ = (this.nextFeed_ == '');
-
-    this.onNewEntries(entries);
-  }).bind(this);
-
-  var searchParams = {
-    'query': this.query_,
-    'nextFeed': this.nextFeed_
-  };
-  chrome.fileBrowserPrivate.searchDrive(searchParams, searchCallback);
+  this.scanner_ = new DriveSearchContentScanner(this.query_);
+  this.scanner_.scan(this.onNewEntries.bind(this),
+                     this.onScanCompleted.bind(this),
+                     this.onScanError.bind(this));
 };
 
-
 /**
  * @param {FileListContext} context File list context.
  * @param {DirectoryEntry} dirEntry Current directory.
@@ -564,7 +814,7 @@ DirectoryContentsDriveSearch.prototype.readNextChunk = function() {
 function DirectoryContentsLocalSearch(context, dirEntry, query) {
   DirectoryContents.call(this, context);
   this.directoryEntry_ = dirEntry;
-  this.query_ = query.toLowerCase();
+  this.query_ = query;
 }
 
 /**
@@ -610,72 +860,11 @@ DirectoryContentsLocalSearch.prototype.getLastNonSearchDirectoryEntry =
  * 'scan-failed' event will be fired upon completion.
  */
 DirectoryContentsLocalSearch.prototype.scan = function() {
-  this.pendingScans_ = 0;
-  this.scanDirectory_(this.directoryEntry_);
-};
-
-/**
- * Scan a directory.
- * @param {DirectoryEntry} entry A directory to scan.
- * @private
- */
-DirectoryContentsLocalSearch.prototype.scanDirectory_ = function(entry) {
-  this.pendingScans_++;
-  var reader = entry.createReader();
-  var found = [];
-
-  var onChunkComplete = function(entries) {
-    if (this.scanCancelled_)
-      return;
-
-    if (entries.length === 0) {
-      if (found.length > 0)
-        this.onNewEntries(found);
-      this.pendingScans_--;
-      if (this.pendingScans_ === 0)
-        this.lastChunkReceived();
-      return;
-    }
-
-    for (var i = 0; i < entries.length; i++) {
-      if (entries[i].name.toLowerCase().indexOf(this.query_) != -1) {
-        found.push(entries[i]);
-      }
-
-      if (entries[i].isDirectory)
-        this.scanDirectory_(entries[i]);
-    }
-
-    getNextChunk();
-  }.bind(this);
-
-  var getNextChunk = function() {
-    reader.readEntries(onChunkComplete, this.onError.bind(this));
-  }.bind(this);
-
-  getNextChunk();
-};
-
-/**
- * We get results for each directory in one go in scanDirectory_.
- */
-DirectoryContentsLocalSearch.prototype.readNextChunk = function() {
-};
-
-/**
- * List of search types for DirectoryContentsDriveSearch.
- * TODO(haruki): SHARED_WITH_ME support for searchDriveMetadata is not yet
- * implemented. Update this when it's done.
- * SEARCH_ALL uses no filtering.
- * SEARCH_SHARED_WITH_ME searches for the shared-with-me entries.
- * SEARCH_RECENT_FILES searches for recently accessed file entries.
- * @enum {number}
- */
-DirectoryContentsDriveSearchMetadata.SearchType = {
-  SEARCH_ALL: 0,
-  SEARCH_SHARED_WITH_ME: 1,
-  SEARCH_RECENT_FILES: 2,
-  SEARCH_OFFLINE: 3
+  this.scanner_ =
+      new LocalSearchContentScanner(this.directoryEntry_, this.query_);
+  this.scanner_.scan(this.onNewEntries.bind(this),
+                     this.onScanCompleted.bind(this),
+                     this.onScanError.bind(this));
 };
 
 /**
@@ -686,7 +875,7 @@ DirectoryContentsDriveSearchMetadata.SearchType = {
  * @param {DirectoryEntry} fakeDirEntry Fake directory representing the set of
  *     result files. This serves as a top directory for this search.
  * @param {string} query Search query to filter the files.
- * @param {DirectoryContentsDriveSearchMetadata.SearchType} searchType
+ * @param {DriveMetadataSearchContentScanner.SearchType} searchType
  *     Type of search. searchDriveMetadata will restricts the entries based on
  *     the given search type.
  * @constructor
@@ -749,56 +938,9 @@ DirectoryContentsDriveSearchMetadata.prototype.getLastNonSearchDirectoryEntry =
  * 'scan-failed' event will be fired upon completion.
  */
 DirectoryContentsDriveSearchMetadata.prototype.scan = function() {
-  this.readNextChunk();
-};
-
-/**
- * All the results are read in one chunk, so when we try to read second chunk,
- * it means we're done.
- */
-DirectoryContentsDriveSearchMetadata.prototype.readNextChunk = function() {
-  if (this.scanCancelled_)
-    return;
-
-  if (this.done_) {
-    this.lastChunkReceived();
-    return;
-  }
-
-  var searchCallback = (function(results, nextFeed) {
-    if (!results) {
-      console.error('Drive search encountered an error.');
-      this.lastChunkReceived();
-      return;
-    }
-    this.done_ = true;
-
-    var entries = results.map(function(r) { return r.entry; });
-    this.onNewEntries(entries);
-    this.lastChunkReceived();
-  }).bind(this);
-
-  var type;
-  switch (this.searchType_) {
-    case DirectoryContentsDriveSearchMetadata.SearchType.SEARCH_ALL:
-      type = 'ALL';
-      break;
-    case DirectoryContentsDriveSearchMetadata.SearchType.SEARCH_SHARED_WITH_ME:
-      type = 'SHARED_WITH_ME';
-      break;
-    case DirectoryContentsDriveSearchMetadata.SearchType.SEARCH_RECENT_FILES:
-      type = 'EXCLUDE_DIRECTORIES';
-      break;
-    case DirectoryContentsDriveSearchMetadata.SearchType.SEARCH_OFFLINE:
-      type = 'OFFLINE';
-      break;
-    default:
-      throw Error('Unknown search type: ' + this.searchType_);
-  }
-  var searchParams = {
-    'query': this.query_,
-    'types': type,
-    'maxResults': 500
-  };
-  chrome.fileBrowserPrivate.searchDriveMetadata(searchParams, searchCallback);
+  this.scanner_ =
+      new DriveMetadataSearchContentScanner(this.query_, this.searchType_);
+  this.scanner_.scan(this.onNewEntries.bind(this),
+                     this.onScanCompleted.bind(this),
+                     this.onScanError.bind(this));
 };