Introduce Position::inDocument()

Source/core/editing/DeleteSelectionCommand.cpp

Index: Source/core/editing/DeleteSelectionCommand.cpp
diff --git a/Source/core/editing/DeleteSelectionCommand.cpp b/Source/core/editing/DeleteSelectionCommand.cpp
index be256e602f54583cfa4821d54cd46738f2264b70..164437e8c25f02fbdaae9d5b7c15953e54cbb0e3 100644
--- a/Source/core/editing/DeleteSelectionCommand.cpp
+++ b/Source/core/editing/DeleteSelectionCommand.cpp
@@ -532,7 +532,7 @@ void DeleteSelectionCommand::handleGeneralDelete()
             }
         }
 
-        if (m_downstreamEnd.deprecatedNode() != startNode && !m_upstreamStart.deprecatedNode()->isDescendantOf(m_downstreamEnd.deprecatedNode()) && m_downstreamEnd.anchorNode()->inDocument() && m_downstreamEnd.deprecatedEditingOffset() >= caretMinOffset(m_downstreamEnd.deprecatedNode())) {
+        if (m_downstreamEnd.deprecatedNode() != startNode && !m_upstreamStart.deprecatedNode()->isDescendantOf(m_downstreamEnd.deprecatedNode()) && m_downstreamEnd.inDocument() && m_downstreamEnd.deprecatedEditingOffset() >= caretMinOffset(m_downstreamEnd.deprecatedNode())) {
             if (m_downstreamEnd.atLastEditingPositionForNode() && !canHaveChildrenForEditing(m_downstreamEnd.deprecatedNode())) {
                 // The node itself is fully selected, not just its contents.  Delete it.
                 removeNode(m_downstreamEnd.deprecatedNode());
@@ -549,7 +549,7 @@ void DeleteSelectionCommand::handleGeneralDelete()
                 // know how many children to remove.
                 // FIXME: Make m_upstreamStart a position we update as we remove content, then we can
                 // always know which children to remove.
-                } else if (!(startNodeWasDescendantOfEndNode && !m_upstreamStart.anchorNode()->inDocument())) {
+                } else if (!(startNodeWasDescendantOfEndNode && !m_upstreamStart.inDocument())) {
                     int offset = 0;
                     if (m_upstreamStart.deprecatedNode()->isDescendantOf(m_downstreamEnd.deprecatedNode())) {
                         Node* n = m_upstreamStart.deprecatedNode();
@@ -601,7 +601,7 @@ void DeleteSelectionCommand::mergeParagraphs()
     ASSERT(!m_pruneStartBlockIfNecessary);
 
     // FIXME: Deletion should adjust selection endpoints as it removes nodes so that we never get into this state (4099839).
-    if (!m_downstreamEnd.anchorNode()->inDocument() || !m_upstreamStart.anchorNode()->inDocument())
+    if (!m_downstreamEnd.inDocument() || !m_upstreamStart.inDocument())
          return;
 
     // FIXME: The deletion algorithm shouldn't let this happen.