Issue #2458 - Make HTMLInputElement.files read-write

Resolves #2458

dom/html/HTMLInputElement.cpp

@@ -3105,6 +3105,26 @@ HTMLInputElement::GetFiles()
   return mFileList;
 }
 
+void
+HTMLInputElement::SetFiles(FileList* aFiles)
+{
+  if (mType != NS_FORM_INPUT_FILE || !aFiles) {
+    return;
+  }
+
+  // Clear |mFileList| to omit |UpdateFileList|
+  if (mFileList) {
+    mFileList->Clear();
+    mFileList = nullptr;
+  }
+
+  // Update |mFilesOrDirectories|
+  SetFiles(aFiles, true);
+
+  // Update |mFileList| without copy
+  mFileList = aFiles;
+}
+
 /* static */ void
 HTMLInputElement::HandleNumberControlSpin(void* aData)
 {

dom/html/HTMLInputElement.h

@@ -474,6 +474,7 @@ public:
   // XPCOM GetForm() is OK
 
   FileList* GetFiles();
+  void SetFiles(FileList* aFiles);
 
   // XPCOM GetFormAction() is OK
   void SetFormAction(const nsAString& aValue, ErrorResult& aRv)

dom/webidl/HTMLInputElement.webidl

@@ -40,7 +40,7 @@ interface HTMLInputElement : HTMLElement {
            attribute boolean disabled;
   readonly attribute HTMLFormElement? form;
   [Pure]
-  readonly attribute FileList? files;
+           attribute FileList? files;
   [CEReactions, Pure, SetterThrows]
            attribute DOMString formAction;
   [CEReactions, Pure, SetterThrows]