Show a local folder's size in QuickView.

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

Index: ui/file_manager/file_manager/foreground/js/metadata_box_controller.js
diff --git a/ui/file_manager/file_manager/foreground/js/metadata_box_controller.js b/ui/file_manager/file_manager/foreground/js/metadata_box_controller.js
index 94d8bc8b21446b735103a799aa671dc65d4788bd..6d0b286dc4e652f2a734f3e9248d3b017b438932 100644
--- a/ui/file_manager/file_manager/foreground/js/metadata_box_controller.js
+++ b/ui/file_manager/file_manager/foreground/js/metadata_box_controller.js
@@ -90,7 +90,7 @@ MetadataBoxController.prototype.updateView_ = function() {
  * Update metadata box with general file information.
  * Then retrieve file specific metadata if any.
  *
- * @param {!FileEntry} entry
+ * @param {!Entry} entry
  * @param {!Array<!MetadataItem>} items
  *
  * @private
@@ -105,6 +105,9 @@ MetadataBoxController.prototype.onGeneralMetadataLoaded_ = function(
     this.metadataBox_.size =
         this.fileMetadataFormatter_.formatSize(item.size, item.hosted);
   }
+  if (entry.isDirectory) {
+    this.setDirectorySize_( /** @type {!DirectoryEntry} */ (entry));
+  }
   if (item.modificationTime) {
     this.metadataBox_.modificationTime =
         this.fileMetadataFormatter_.formatModDate(item.modificationTime);
@@ -147,3 +150,31 @@ MetadataBoxController.prototype.onGeneralMetadataLoaded_ = function(
     }
   }
 };
+
+/**
+ * Set a current directory's size in metadata box.
+ *
+ * @param {!DirectoryEntry} entry
+ *
+ * @private
+ */
+MetadataBoxController.prototype.setDirectorySize_ = function(entry) {
+  if (!entry.isDirectory)
+    return;
+
+  this.metadataBox_.isSizeLoading = true;
+  chrome.fileManagerPrivate.getDirectorySize(entry,
+      function(size) {
+        if(this.quickViewModel_.getSelectedEntry() != entry) {
+          return;
+        }
+        if(chrome.runtime.lastError) {
+          this.metadataBox_.isSizeLoading = false;
+          return;
+        }
+
+        this.metadataBox_.isSizeLoading = false;
+        this.metadataBox_.size =
+        this.fileMetadataFormatter_.formatSize(size, true);
+      }.bind(this));
+};