Convert an assertion to if-condition in ReplaceSelectionCommand::doApply()

third_party/WebKit/Source/core/editing/commands/ReplaceSelectionCommand.cpp

Index: third_party/WebKit/Source/core/editing/commands/ReplaceSelectionCommand.cpp
diff --git a/third_party/WebKit/Source/core/editing/commands/ReplaceSelectionCommand.cpp b/third_party/WebKit/Source/core/editing/commands/ReplaceSelectionCommand.cpp
index 0003284950c9157f204502f4c97f3429eca29054..16f62db723846de5faf1a9c31f4e7d46651da523 100644
--- a/third_party/WebKit/Source/core/editing/commands/ReplaceSelectionCommand.cpp
+++ b/third_party/WebKit/Source/core/editing/commands/ReplaceSelectionCommand.cpp
@@ -1148,7 +1148,6 @@ void ReplaceSelectionCommand::doApply(EditingState* editingState)
     // Adjust insertionPos to prevent nesting.
     // If the start was in a Mail blockquote, we will have already handled adjusting insertionPos above.
     if (m_preventNesting && enclosingBlockOfInsertionPos && !isTableCell(enclosingBlockOfInsertionPos) && !startIsInsideMailBlockquote) {
-        DCHECK_NE(enclosingBlockOfInsertionPos, currentRoot);

[Xiaocheng, 2016/09/12 04:58:56]

What's the reason the assertion was introduced? Is there any buggy behavior that
it's trying to detect?

[yosin_UTC9, 2016/09/12 05:21:38]

This assertion is introduced by https://bugs.webkit.org/show_bug.cgi?id=8592
It seems this assertion is correct, we should not adjust
|enclosingBlockOfInsertionPos| when |enclosingBlockOfInsertionPos ==
currentRoot|.

         VisiblePosition visibleInsertionPos = createVisiblePosition(insertionPos);
         if (isEndOfBlock(visibleInsertionPos) && !(isStartOfBlock(visibleInsertionPos) && fragment.hasInterchangeNewlineAtEnd()))
             insertionPos = Position::inParentAfterNode(*enclosingBlockOfInsertionPos);