Rename DriveProvider to ExternalProvider.

ui/file_manager/gallery/js/mosaic_mode.js

Index: ui/file_manager/gallery/js/mosaic_mode.js
diff --git a/ui/file_manager/gallery/js/mosaic_mode.js b/ui/file_manager/gallery/js/mosaic_mode.js
index 78af4d850dcf862ddb093100c611830646413fc1..ccf12536493ceed236812787cfcdf81a72b779a3 100644
--- a/ui/file_manager/gallery/js/mosaic_mode.js
+++ b/ui/file_manager/gallery/js/mosaic_mode.js
@@ -1783,10 +1783,10 @@ Mosaic.Tile.prototype.init = function() {
   if (metadata.media && metadata.media.width) {
     width = metadata.media.width;
     height = metadata.media.height;
-  } else if (metadata.drive && metadata.drive.imageWidth &&
-             metadata.drive.imageHeight) {
-    width = metadata.drive.imageWidth;
-    height = metadata.drive.imageHeight;
+  } else if (metadata.external && metadata.external.imageWidth &&
+             metadata.external.imageHeight) {
+    width = metadata.external.imageWidth;
+    height = metadata.external.imageHeight;
   } else {
     // No dimensions in metadata, then use the generic dimensions.
     width = Mosaic.Tile.GENERIC_ICON_SIZE;