Make FrameSelection::SelectAll bail if 'selectstart' detaches frame

third_party/WebKit/Source/core/editing/FrameSelection.cpp

Index: third_party/WebKit/Source/core/editing/FrameSelection.cpp
diff --git a/third_party/WebKit/Source/core/editing/FrameSelection.cpp b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
index 87ec20377a9264488e300255fbd46ffb3ea3af8e..c29027dd0a1dd11bf29fa63735e9e3ee60b32b52 100644
--- a/third_party/WebKit/Source/core/editing/FrameSelection.cpp
+++ b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
@@ -658,6 +658,11 @@ void FrameSelection::SelectAll() {
     if (select_start_target->DispatchEvent(Event::CreateCancelableBubble(
             EventTypeNames::selectstart)) != DispatchEventResult::kNotCanceled)
       return;
+    // The frame may be detached due to selectstart event.
+    if (!IsAvailable()) {
+      // Reached by editing/selection/selectstart_detach_frame.html
+      return;
+    }
     // |root| may be detached due to selectstart event.
     if (!root->isConnected() || expected_document != root->GetDocument())
       return;