Add WebScopedAXContext to allow a one-time snapshot of accessibility.

Source/modules/accessibility/InspectorAccessibilityAgent.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "modules/accessibility/InspectorAccessibilityAgent.h"
 
 #include "core/dom/AXObjectCache.h"
 #include "core/dom/DOMNodeIds.h"
@@ skipping 407 matching lines @@
 
     InspectorDOMAgent* domAgent = toLocalFrame(mainFrame)->instrumentingAgents()->inspectorDOMAgent();
     if (!domAgent) {
         *errorString = "DOM agent must be enabled";
         return;
     }
     Node* node = domAgent->assertNode(errorString, nodeId);
     if (!node)
         return;
     Document& document = node->document();
-    ScopedAXObjectCache cache(document);
-    AXObjectCacheImpl* cacheImpl = toAXObjectCacheImpl(cache.get());
+    RefPtr<ScopedAXObjectCache> cache(adoptRef(new ScopedAXObjectCache(document)));
+    AXObjectCacheImpl* cacheImpl = toAXObjectCacheImpl(cache->get());
     AXObject* axObject = cacheImpl->getOrCreate(node);
     if (!axObject)
         return;
 
     RefPtr<TypeBuilder::Array<AXProperty>> properties = TypeBuilder::Array<AXProperty>::create();
     fillLiveRegionProperties(axObject, properties);
     fillGlobalStates(axObject, properties);
     fillWidgetProperties(axObject, properties);
     fillWidgetStates(axObject, properties);
     fillRelationships(axObject, properties);
 
     accessibilityNode = buildObjectForNode(node, axObject, cacheImpl, properties);
 }
 
 DEFINE_TRACE(InspectorAccessibilityAgent)
 {
     visitor->trace(m_page);
     InspectorBaseAgent::trace(visitor);
 }
 
 } // namespace blink