Prune ComputeVisibleSelectionInDOMTreeDeprecated from RemoveFormatCommand

This patch prunes a call site of the deprecated function, which is safe
because layout is already updated in CompositeEditCommand::Apply().

Bug: 698633
Change-Id: I83c46588c07ce85b5cc765f9b080f356bcbb5885
Reviewed-on: https://chromium-review.googlesource.com/767849Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516388}

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

@@ -57,17 +57,18 @@ static bool IsElementForRemoveFormatCommand(const Element* element) {
 }
 
 void RemoveFormatCommand::DoApply(EditingState* editing_state) {
+  DCHECK(!GetDocument().NeedsLayoutTreeUpdate());
+
+  // TODO(editing-dev): Stop accessing FrameSelection in edit commands.
   LocalFrame* frame = GetDocument().GetFrame();
   const VisibleSelection selection =
-      frame->Selection().ComputeVisibleSelectionInDOMTreeDeprecated();
+      frame->Selection().ComputeVisibleSelectionInDOMTree();
   if (selection.IsNone() || !selection.IsValidFor(GetDocument()))
     return;
 
   // Get the default style for this editable root, it's the style that we'll
   // give the content that we're operating on.
-  Element* root = frame->Selection()
-                      .ComputeVisibleSelectionInDOMTreeDeprecated()
-                      .RootEditableElement();
+  Element* root = selection.RootEditableElement();
   EditingStyle* default_style = EditingStyle::Create(root);
 
   // We want to remove everything but transparent background.