Do not trigger layout in PasswordAutofillAgent::DidFinishDocumentLoad

components/autofill/content/renderer/form_autofill_util.h

Index: components/autofill/content/renderer/form_autofill_util.h
diff --git a/components/autofill/content/renderer/form_autofill_util.h b/components/autofill/content/renderer/form_autofill_util.h
index d7cb557b05c8928406762778381efc677ca34af9..7f2391dcbf731582d143896e87c92f456e35e664 100644
--- a/components/autofill/content/renderer/form_autofill_util.h
+++ b/components/autofill/content/renderer/form_autofill_util.h
@@ -9,6 +9,7 @@
 
 #include <vector>
 
+#include "base/macros.h"
 #include "base/strings/string16.h"
 #include "components/autofill/core/common/autofill_constants.h"
 #include "components/autofill/core/common/password_form_field_prediction_map.h"
@@ -57,6 +58,22 @@ enum ExtractMask {
 // Copied to components/autofill/ios/browser/resources/autofill_controller.js.
 extern const size_t kMaxParseableFields;
 
+// Create an instance of ScopedLayoutPreventer to stop form_util code from
+// triggering layout as a side-effect. For example, when creating a
+// FormFieldData, a call to WebNode::isFocusable is normally made, which may
+// trigger a layout computation. When an instance of ScopedLayoutPreventer is
+// alive, that call will not be made. On destruction, this class allows
+// layout-triggering calls again. It is not thread safe and multiple instances
+// should not be created at the same time in the same process.
+class ScopedLayoutPreventer {
+ public:
+  ScopedLayoutPreventer();
+  ~ScopedLayoutPreventer();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ScopedLayoutPreventer);
+};
+
 // Extract FormData from the form element and return whether the operation was
 // successful.
 bool ExtractFormData(const blink::WebFormElement& form_element, FormData* data);