[directorytree] Use FSP and DOCUMENT_PROVIDERS generic icons if needed

The iconSet property of most volume types is empty, but we expect that
third party volumes (ANDROID_FILES, DOCUMENT_PROVIDERS and File System
Providers) should provide icons in their respective iconSets.

CL:2032469 added a shouldProvideIcons() helper to volume manager so we
can detect these volumes. ANDROID_FILES is done (CL:1945958) and noted
File System Providers and DOCUMENT_PROVIDERS were still todo.

In this change, use the shouldProvideIcons() helper to detect the File
System Providers and DOCUMENT_PROVIDERS that provide no icons, and use
a generic icon for these volumes instead.

files-ng only: this to avoid drawing a dull gray box for these volumes
in files-ng if they provide no icons.

Bug: 992819
Change-Id: Ia2b4c6caf70d3b8250acc8d9706f476a486199ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2089178Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747474}

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

@@ -1178,6 +1178,10 @@ class VolumeItem extends DirectoryItem {
         util.iconSetToCSSBackgroundImageValue(volumeInfo.iconSet);
     if (backgroundImage !== 'none') {
       icon.setAttribute('style', 'background-image: ' + backgroundImage);
+    } else if (directorytree.FILES_NG_ENABLED) {
+      if (VolumeManagerCommon.shouldProvideIcons(volumeInfo.volumeType)) {
+        icon.setAttribute('use-generic-provided-icon', '');
+      }
     }
 
     icon.setAttribute('volume-type-icon', volumeInfo.volumeType);