Enumerate the return value of dispatchEvent so it is clear.

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 55 matching lines @@
 
 namespace {
 
 void setSelectionIfNeeded(FrameSelection& selection, const VisibleSelectionInFlatTree& newSelection)
 {
     if (selection.visibleSelection<EditingInFlatTreeStrategy>() == newSelection)
         return;
     selection.setSelection(newSelection);
 }
 
-bool dispatchSelectStart(Node* node)
+DispatchEventResult dispatchSelectStart(Node* node)
 {
     if (!node || !node->layoutObject())
-        return true;
+        return DispatchEventResult::NotCanceled;
 
     return node->dispatchEvent(Event::createCancelableBubble(EventTypeNames::selectstart));
 }
 
 VisibleSelectionInFlatTree expandSelectionToRespectUserSelectAll(Node* targetNode, const VisibleSelectionInFlatTree& selection)
 {
     Node* rootUserSelectAll = EditingInFlatTreeStrategy::rootUserSelectAllForNode(targetNode);
     if (!rootUserSelectAll)
         return selection;
 
@@ skipping 120 matching lines @@
     // FIXME: Isn't there a better non-SVG-specific way to do this?
     if (Node* selectionBaseNode = newSelection.base().anchorNode()) {
         if (LayoutObject* selectionBaseLayoutObject = selectionBaseNode->layoutObject()) {
             if (selectionBaseLayoutObject->isSVGText()) {
                 if (target->layoutObject()->containingBlock() != selectionBaseLayoutObject->containingBlock())
                     return;
             }
         }
     }
 
-    if (m_selectionState == SelectionState::HaveNotStartedSelection && !dispatchSelectStart(target))
+    if (m_selectionState == SelectionState::HaveNotStartedSelection && dispatchSelectStart(target) != DispatchEventResult::NotCanceled)
         return;
 
     // TODO(yosin) We should check |mousePressNode|, |targetPosition|, and
     // |newSelection| are valid for |m_frame->document()|.
     // |dispatchSelectStart()| can change them by "selectstart" event handler.
 
     if (m_selectionState != SelectionState::ExtendedSelection) {
         // Always extend selection here because it's caused by a mouse drag
         m_selectionState = SelectionState::ExtendedSelection;
         newSelection = VisibleSelectionInFlatTree(targetPosition);
@@ skipping 31 matching lines @@
 
     selection().setNonDirectionalSelectionIfNeeded(newSelection, selection().granularity(),
         FrameSelection::AdjustEndpointsAtBidiBoundary);
 }
 
 bool SelectionController::updateSelectionForMouseDownDispatchingSelectStart(Node* targetNode, const VisibleSelectionInFlatTree& selection, TextGranularity granularity)
 {
     if (targetNode && targetNode->layoutObject() && !targetNode->layoutObject()->isSelectable())
         return false;
 
-    if (!dispatchSelectStart(targetNode))
+    if (dispatchSelectStart(targetNode) != DispatchEventResult::NotCanceled)
         return false;
 
     if (!selection.isValidFor(*m_frame->document()))
         return false;
 
     if (selection.isRange()) {
         m_selectionState = SelectionState::ExtendedSelection;
     } else {
         granularity = CharacterGranularity;
         m_selectionState = SelectionState::PlacedCaret;
@@ skipping 334 matching lines @@
     else
         m_selectionState = SelectionState::HaveNotStartedSelection;
 }
 
 FrameSelection& SelectionController::selection() const
 {
     return m_frame->selection();
 }
 
 } // namespace blink