Revert of RenderFlexibleBox should be treated as a candidate for visi…

…ble position. (patchset #1 id:1 of https://codereview.chromium.org/897633002/)

Reason for revert:
Revert for now until the fix is ready. Will also be reverted on release branch.

Original issue's description:
> RenderFlexibleBox should be treated as a candidate for visible position.
> 
> Visible selection in an editable area is recalculated whenever an inner value of div is changed.
> If the inner value is empty, the visible selection recalculated with DeleteSelectionCommand::m_endingPostion
> is not correct. Because RenderBlockFlow is only considered but not RenderFlexibleBox in Position::isCandidate
> so that a calculated ending VisiblePosition for an editable div having ‘display : flex’ goes weird
> and VisibleSelection is empty accordingly.
> 
> BUG=450617
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=189482

TBR=sigbjornf@opera.com,rego@igalia.com,shivamidow@gmail.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=450617

Review URL: https://codereview.chromium.org/1060113002

git-svn-id: svn://svn.chromium.org/blink/trunk@193212 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Source/core/dom/Position.cpp

@@ -891,7 +891,7 @@ bool Position::isCandidate() const
     if (isHTMLHtmlElement(*m_anchorNode))
         return false;
 
-    if (renderer->isLayoutBlockFlow() || renderer->isFlexibleBox() || renderer->isLayoutGrid()) {
+    if (renderer->isLayoutBlockFlow() || renderer->isLayoutGrid()) {
         if (toLayoutBlock(renderer)->logicalHeight() || isHTMLBodyElement(*m_anchorNode)) {
             if (!Position::hasRenderedNonAnonymousDescendantsWithHeight(renderer))
                 return atFirstEditingPositionForNode() && !Position::nodeIsUserSelectNone(deprecatedNode());