Get rid of obsolete FrameView::m_shouldUpdateViewportIntersection.

third_party/WebKit/Source/core/dom/IntersectionObserver.cpp

 // Copyright 2016 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 "core/dom/IntersectionObserver.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/css/parser/CSSParserTokenRange.h"
 #include "core/css/parser/CSSTokenizer.h"
 #include "core/dom/Element.h"
@@ skipping 202 matching lines @@
   IgnorableExceptionState exceptionState;
   disconnect(exceptionState);
   m_root = nullptr;
 }
 
 bool IntersectionObserver::rootIsValid() const {
   return rootIsImplicit() || root();
 }
 
 Document& IntersectionObserver::trackingDocument() const {
-  Document* document = nullptr;
   if (rootIsImplicit()) {
     DCHECK(m_callback->getExecutionContext());
-    document = toDocument(m_callback->getExecutionContext());
-  } else {
-    DCHECK(root());
-    document = &root()->document();
+    return *toDocument(m_callback->getExecutionContext());
   }
-  DCHECK(document);
-  DCHECK(document->frame());
-  return *document->frame()->localFrameRoot()->document();
+  DCHECK(root());
+  return root()->document();
 }
 
 void IntersectionObserver::observe(Element* target,
                                    ExceptionState& exceptionState) {
   if (!rootIsValid()) {
     exceptionState.throwDOMException(
         InvalidStateError,
         "observe() called on an IntersectionObserver with an invalid root.");
     return;
   }
@@ skipping 163 matching lines @@
 
 DEFINE_TRACE(IntersectionObserver) {
   visitor->template registerWeakMembers<
       IntersectionObserver, &IntersectionObserver::clearWeakMembers>(this);
   visitor->trace(m_callback);
   visitor->trace(m_observations);
   visitor->trace(m_entries);
 }
 
 }  // namespace blink