Reuse File objects in FileTransferController.

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

Index: ui/file_manager/file_manager/foreground/js/file_transfer_controller.js
diff --git a/ui/file_manager/file_manager/foreground/js/file_transfer_controller.js b/ui/file_manager/file_manager/foreground/js/file_transfer_controller.js
index 35ecd10b61ec694a1f9da2a66a4438a4b6fd9a87..10156bd01a260dea7a611df09368538f6629574c 100644
--- a/ui/file_manager/file_manager/foreground/js/file_transfer_controller.js
+++ b/ui/file_manager/file_manager/foreground/js/file_transfer_controller.js
@@ -1261,7 +1261,16 @@ FileTransferController.prototype.simulateCommand_ = function(command, handler) {
  */
 FileTransferController.prototype.onFileSelectionChanged_ = function() {
   this.preloadedThumbnailImagePromise_ = null;
-  this.selectedAsyncData_ = {};
+  // Remove file objects that are no longer in the selection.

[fukino, 2017/04/26 07:14:31]

It might be better to place this logic in onFileSelectionChangedThrottled_.

When a user select the first entry and keep pressing Shift + DOWN, this method
will take O(n^2).

[tetsui2, 2017/04/26 07:42:31]

Done.

+  var newSelectedAsyncData = {};
+  var entries = this.selectionHandler_.selection.entries;
+  for (var i = 0; i < entries.length; i++) {
+    var entryUrl = entries[i].toURL();
+    if (entryUrl in this.selectedAsyncData_) {
+      newSelectedAsyncData[entryUrl] = this.selectedAsyncData_[entryUrl];
+    }
+  }
+  this.selectedAsyncData_ = newSelectedAsyncData;
 };
 
 /**
@@ -1274,7 +1283,9 @@ FileTransferController.prototype.onFileSelectionChangedThrottled_ = function() {
   for (var i = 0; i < entries.length; i++) {
     if (entries[i].isFile)
       fileEntries.push(entries[i]);
-    asyncData[entries[i].toURL()] = {externalFileUrl: '', file: null};
+    if (!(entries[i].toURL() in asyncData)) {
+      asyncData[entries[i].toURL()] = {externalFileUrl: '', file: null};
+    }
   }
   var containsDirectory = this.selectionHandler_.selection.directoryCount > 0;
 
@@ -1285,9 +1296,11 @@ FileTransferController.prototype.onFileSelectionChangedThrottled_ = function() {
   if (!containsDirectory) {
     for (var i = 0; i < fileEntries.length; i++) {
       (function(fileEntry) {
-        fileEntry.file(function(file) {
-          asyncData[fileEntry.toURL()].file = file;
-        });
+        if (!(asyncData[fileEntry.toURL()].file)) {
+          fileEntry.file(function(file) {
+            asyncData[fileEntry.toURL()].file = file;
+          });
+        }
       })(fileEntries[i]);
     }
   }