First-cut at fixing unhandled Tap event returns in Blink.

Source/core/page/EventHandler.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)
  *
  * 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
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 457 matching lines @@
 
     return updateSelectionForMouseDownDispatchingSelectStart(innerNode, expandSelectionToRespectUserSelectAll(innerNode, newSelection), ParagraphGranularity);
 }
 
 static int textDistance(const Position& start, const Position& end)
 {
     RefPtrWillBeRawPtr<Range> range = Range::create(*start.document(), start, end);
     return TextIterator::rangeLength(range.get(), true);
 }
 
+static bool isInteractiveNode(Node* node)
+{
+    if (!node)
+        return false;
+    // Editable nodes are always interactive.
+    if (node->rendererIsEditable())
+        return true;
+    // TODO(donnd): check for other indications of interactivity, including control elements and ARIA roles.
+    return false;
+}
+
 bool EventHandler::handleMousePressEventSingleClick(const MouseEventWithHitTestResults& event)
 {
     TRACE_EVENT0("webkit", "EventHandler::handleMousePressEventSingleClick");
 
     m_frame->document()->updateLayoutIgnorePendingStylesheets();
     Node* innerNode = event.targetNode();
     if (!(innerNode && innerNode->renderer() && m_mouseDownMayStartSelect))
         return false;
 
     // Extend the selection if the Shift key is down, unless the click is in a link.
@@ skipping 43 matching lines @@
             newSelection.setExtent(pos);
 
         if (m_frame->selection().granularity() != CharacterGranularity) {
             granularity = m_frame->selection().granularity();
             newSelection.expandUsingGranularity(m_frame->selection().granularity());
         }
     } else {
         newSelection = expandSelectionToRespectUserSelectAll(innerNode, VisibleSelection(visiblePos));
     }
 
-    bool handled = updateSelectionForMouseDownDispatchingSelectStart(innerNode, newSelection, granularity);
-    return handled;
+    updateSelectionForMouseDownDispatchingSelectStart(innerNode, newSelection, granularity);

[Rick Byers, 2014/05/28 17:36:57]

I think this is fine for addressing the original problem you were concerned
with.  Please add a comment saying that we consider updating the selection to be
a side-effect of the event and so it doesn't impact the handled state.

[donnd, 2014/05/31 03:22:55]

Done.

+
+    // If the target node is editable, then it handles the click, either directly or through a handler.

[Rick Byers, 2014/05/28 17:36:57]

Hmm, it seems wrong / error-prone to have this logic separately from what is
actually handling the event.  Ideally the code that sets the handled state
should be in the exact same place as the code that is actually doing the
handling.  So, for example, where are mouse events actually handled by
content-editable nodes?

Remember you've got a few events here (mousedown, mouseup, click) - are you sure
it's just the mousedown (that we're dealing with in this function) that editable
nodes handle?  Or maybe it's actually the mouseup or click whose handled state
should be corrected?

[donnd, 2014/05/31 03:22:55]

For now, we just always return false.  That should help us figure out if this
change will break anything.

+    return isInteractiveNode(event.targetNode());
 }
 
 static inline bool canMouseDownStartSelect(Node* node)
 {
     if (!node || !node->renderer())
         return true;
 
     if (!node->canStartSelection())
         return false;
 
@@ skipping 3176 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace WebCore