Make Editor::appliedEditing update layout before changing selection

Updating frame selection currently requires clean layout, as it calls
mostBackwardCaretPosition through SelectionAdjuster. One code path that
violates it is from Editor::appliedEditing, which is fixed by this patch.

BUG=679616

Review-Url: https://codereview.chromium.org/2626933002
Cr-Commit-Position: refs/heads/master@{#442881}

third_party/WebKit/LayoutTests/editing/pasteboard/copy-paste-underlined.html

@@ -25,4 +25,27 @@ test(() => {
         '<div contenteditable id="paste"><u>foo bar baz.|</u></div>'
       ].join(''));
   }, 'Copy/paste underlined text.');
+
+test(() => {
+  assert_not_equals(
+      window.testRunner, undefined,
+     'This test requires testRunner.');
+
+  assert_selection(
+      [
+        '<div contenteditable spellcheck="false">^foo bar baz.|</div>',
+        '<div contenteditable id="paste"><br></div>'
+      ].join(''),
+      selection => {
+        const document = selection.document;
+        document.execCommand('underline');
+        document.execCommand('copy');
+        document.getElementById('paste').focus();
+        document.execCommand('paste');
+      },
+      [
+        '<div contenteditable spellcheck="false"><u>foo bar baz.</u></div>',
+        '<div contenteditable id="paste"><u>foo bar baz.|</u></div>'
+      ].join(''));
+  }, 'Copy/paste underlined text with spell checker off.');
 </script>

third_party/WebKit/Source/core/editing/Editor.cpp

@@ -858,6 +858,14 @@ void Editor::appliedEditing(CompositeEditCommand* cmd) {
       composition->startingRootEditableElement(),
       composition->endingRootEditableElement(), cmd->inputType(),
       cmd->textDataForInputEvent(), isComposingFromCommand(cmd));
+
+  // TODO(editing-dev): The use of updateStyleAndLayoutIgnorePendingStylesheets
+  // needs to be audited.  See http://crbug.com/590369 for more details.
+  // The clean layout is consumed by |mostBackwardCaretPosition|, called through
+  // |changeSelectionAfterCommand|. In the long term, we should postpone visible
+  // selection canonicalization so that selection update does not need layout.
+  frame().document()->updateStyleAndLayoutIgnorePendingStylesheets();
+
   VisibleSelection newSelection(cmd->endingSelection());
 
   // Don't clear the typing style with this selection change. We do those things