Implement ShadowRoot.delegatesFocus 2/4 (slide focus on mouse click)

Source/core/input/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 2053 matching lines @@
     // Only change the focus when clicking scrollbars if it can transfered to a
     // mouse focusable node.
     if (!element && targetedEvent.hitTestResult().scrollbar())
         return true;
 
     if (Page* page = m_frame->page()) {
         // If focus shift is blocked, we eat the event. Note we should never
         // clear swallowEvent if the page already set it (e.g., by canceling
         // default behavior).
         if (element) {
+            if (slideFocusOnShadowHostIfNecessary(*element))
+                return true;
             if (!page->focusController().setFocusedElement(element, m_frame, WebFocusTypeMouse))
                 return true;
         } else {
             // We call setFocusedElement even with !element in order to blur
             // current focus element when a link is clicked; this is expected by
             // some sites that rely on onChange handlers running from form
             // fields before the button click is processed.
             if (!page->focusController().setFocusedElement(0, m_frame))
                 return true;
         }
     }
 
     return false;
 }
 
+bool EventHandler::slideFocusOnShadowHostIfNecessary(const Element& element)
+{
+    if (element.shadowRoot() && element.shadowRoot()->delegatesFocus()) {
+        Document* doc = m_frame->document();
+        if (element.containsIncludingShadowDOM(doc->focusedElement())) {
+            // If the inner element is already focused, do nothing.
+            return true;
+        }
+
+        // If the host has a focusable inner element, focus it. Otherwise, the host takes focus.
+        Page* page = m_frame->page();
+        ASSERT(page);
+        Node* next = page->focusController().findFocusableNode(WebFocusTypeForward, *element.shadowRoot());
+        if (next && next->isElementNode() && element.containsIncludingShadowDOM(next)) {
+            // Use WebFocusTypeForward instead of WebFocusTypeMouse here to mean the focus has slided.
+            toElement(next)->focus(false, WebFocusTypeForward);
+            return true;
+        }
+    }
+    return false;
+}
+
 bool EventHandler::handleWheelEvent(const PlatformWheelEvent& event)
 {
 #define RETURN_WHEEL_EVENT_HANDLED() \
     { \
         setFrameWasScrolledByUser(); \
         return true; \
     }
 
     Document* doc = m_frame->document();
 
@@ skipping 2080 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink