Hide .crdownload files and prevent users from changing extension to it.

BUG=409490
TEST=manually

Review URL: https://codereview.chromium.org/528263002

Cr-Commit-Position: refs/heads/master@{#293477}

ui/file_manager/file_manager/common/js/util.js

@@ -1344,6 +1344,8 @@ util.validateFileName = function(parentEntry, name, filterHiddenOn) {
     return Promise.reject(str('ERROR_WHITESPACE_NAME'));
   else if (/^(CON|PRN|AUX|NUL|COM[1-9]|LPT[1-9])$/i.test(name))
     return Promise.reject(str('ERROR_RESERVED_NAME'));
+  else if (filterHiddenOn && /\.crdownload$/i.test(name))
+    return Promise.reject(str('ERROR_RESERVED_NAME'));
   else if (filterHiddenOn && name[0] == '.')
     return Promise.reject(str('ERROR_HIDDEN_NAME'));
 

ui/file_manager/file_manager/foreground/js/directory_contents.js

@@ -319,7 +319,8 @@ DriveMetadataSearchContentScanner.prototype.scan = function(
  * When filters are changed, a 'changed' event is fired.
  *
  * @param {MetadataCache} metadataCache Metadata cache service.
- * @param {boolean} showHidden If files starting with '.' are shown.
+ * @param {boolean} showHidden If files starting with '.' or ending with
+ *     '.crdownlaod' are shown.
  * @constructor
  * @extends {cr.EventTarget}
  */
@@ -371,10 +372,14 @@ FileFilter.prototype.removeFilter = function(name) {
  * @param {boolean} value If do not show hidden files.
  */
 FileFilter.prototype.setFilterHidden = function(value) {
+  var regexpCrdownloadExtension = /\.crdownload$/i;
   if (value) {
     this.addFilter(
         'hidden',
-        function(entry) { return entry.name.substr(0, 1) !== '.'; }
+        function(entry) {
+          return entry.name.substr(0, 1) !== '.' &&
+                 !regexpCrdownloadExtension.test(entry.name);
+        }
     );
   } else {
     this.removeFilter('hidden');

ui/file_manager/file_manager/foreground/js/file_manager.js

@@ -932,7 +932,7 @@ var BOTTOM_MARGIN_FOR_PREVIEW_PANEL_PX = 52;
 
     this.fileFilter_ = new FileFilter(
         this.metadataCache_,
-        false  /* Don't show dot files by default. */);
+        false  /* Don't show dot files and *.crdownload by default. */);
 
     this.fileWatcher_ = new FileWatcher(this.metadataCache_);
     this.fileWatcher_.addEventListener(