Synchronize is-valid flag upon programmatic clearing of file.value

Source/core/html/forms/FileInputType.cpp

Index: Source/core/html/forms/FileInputType.cpp
diff --git a/Source/core/html/forms/FileInputType.cpp b/Source/core/html/forms/FileInputType.cpp
index d85265a183e6cc5519d41c283760763000c63be6..40a753e86bc34e2c5a672a69f38c336d3ff8a42b 100644
--- a/Source/core/html/forms/FileInputType.cpp
+++ b/Source/core/html/forms/FileInputType.cpp
@@ -200,10 +200,14 @@ bool FileInputType::getTypeSpecificValue(String& value)
     return true;
 }
 
-void FileInputType::setValue(const String&, bool, TextFieldEventBehavior)
+void FileInputType::setValue(const String&, bool valueChanged, TextFieldEventBehavior)
 {
+    if (!valueChanged)
+        return;
+
     m_fileList->clear();
     element().setNeedsStyleRecalc();
+    element().setNeedsValidityCheck();
 }
 
 PassRefPtr<FileList> FileInputType::createFileList(const Vector<FileChooserFileInfo>& files) const