Don't toggle image-dominant when the data model is empty.

When adjusting the search parameters, the data model briefly has no
entries. Updating the image-dominant calculation during this interval
causes the image-dominant to be disabled, causing a flicker of the file
names if the contents is image-dominant.

Bug: 483718
Change-Id: I099a013e5f05c36902be67aeffc40edbc718be26
Reviewed-on: https://chromium-review.googlesource.com/c/1341736
Commit-Queue: Sam McNally <sammc@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609228}

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

@@ -669,6 +669,14 @@ FileGrid.prototype.setImportStatusVisible = function(visible) {
  * @private
  */
 FileGrid.prototype.onSplice_ = function() {
+  // When adjusting search parameters, |dataModel| is transiently empty.
+  // Updating whether image-dominant is active at these times can cause spurious
+  // changes. Avoid this problem by not updating whether image-dominant is
+  // active when |dataModel| is empty.
+  if (this.dataModel.getFileCount() == 0 &&
+      this.dataModel.getFolderCount() == 0) {
+    return;
+  }
   this.classList.toggle('image-dominant', this.dataModel.isImageDominant());
 };