Merge 94045 - REGRESSION(r88115): Disabling a file upload control causes an endless busyloop.

Source/WebCore/rendering/RenderFileUploadControl.cpp

Index: Source/WebCore/rendering/RenderFileUploadControl.cpp
===================================================================
--- Source/WebCore/rendering/RenderFileUploadControl.cpp	(revision 94056)
+++ Source/WebCore/rendering/RenderFileUploadControl.cpp	(working copy)
@@ -63,8 +63,15 @@
     HTMLInputElement* input = static_cast<HTMLInputElement*>(node());
     ASSERT(input->isFileUpload());
 
-    if (HTMLInputElement* button = uploadButton())
-        button->setDisabled(!theme()->isEnabled(this));
+    if (HTMLInputElement* button = uploadButton()) {
+        bool newDisabled = !theme()->isEnabled(this);
+        // We should avoid to call HTMLFormControlElement::setDisabled() as
+        // possible because setAttribute() in setDisabled() can cause style
+        // recalculation, and HTMLFormControlElement::recalcStyle() calls
+        // updateFromElement() eventually.
+        if (button->disabled() != newDisabled)
+            button->setDisabled(newDisabled);
+    }
 
     // This only supports clearing out the files, but that's OK because for
     // security reasons that's the only change the DOM is allowed to make.