[Devtools] Accessibility pane: correctly show label text source

third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp

Index: third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
diff --git a/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp b/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
index 58b6cd37e5ce8175a7e970004de4385f78d8dd0f..03ed0b61c7e12905854f2c0e98c30666b1f29701 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
@@ -2259,10 +2259,12 @@ String AXNodeObject::nativeTextAlternative(
            ++labelIndex) {
         Element* label = labels->item(labelIndex);
         if (nameSources) {
-          if (label->getAttribute(forAttr) == htmlElement->getIdAttribute())
+          if (!label->getAttribute(forAttr).isEmpty() &&
+              label->getAttribute(forAttr) == htmlElement->getIdAttribute()) {
             nameSources->back().nativeSource = AXTextFromNativeHTMLLabelFor;
-          else
+          } else {
             nameSources->back().nativeSource = AXTextFromNativeHTMLLabelWrapped;
+          }
         }
         labelElements.push_back(label);
       }