Pass clickEvent to controlElement inside label if targetNode can't start selection

third_party/WebKit/Source/core/html/HTMLLabelElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLLabelElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLLabelElement.cpp b/third_party/WebKit/Source/core/html/HTMLLabelElement.cpp
index 06670f2cf1a1c1623ce571f30741bf5481761a0d..7fc8dbe6160768fabf34a48a6ac32b589a756f21 100644
--- a/third_party/WebKit/Source/core/html/HTMLLabelElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLLabelElement.cpp
@@ -173,7 +173,8 @@ void HTMLLabelElement::DefaultEventHandler(Event* evt) {
                 .IsRange() &&
             !frame->GetEventHandler()
                  .GetSelectionController()
-                 .MouseDownWasSingleClickInSelection())
+                 .MouseDownWasSingleClickInSelection() &&
+            evt->target()->ToNode()->CanStartSelection())

[yosin_UTC9, 2017/05/08 03:25:56]

Regarding a comment of this condition: "Check if there is a selection and click
is not on the selection."
Should we check whether Event#srcElement is LABEL element or not?

           is_label_text_selected = true;
         // If selection is there and is single click i.e. text is
         // selected by dragging over label text, then return.