Make CorrectedSelectionAfterCommand() to check Position offset

This patch changes |CorrectedSelectionAfterCommand()| to use |Position::
IsValidFor()| to make it to check |Position| offset and return valid
selection.

Bug: 873037
Change-Id: I70c7d6f514a39414a4c3245b59969d19beb13f45
Reviewed-on: https://chromium-review.googlesource.com/1170458Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582090}

third_party/blink/renderer/core/editing/commands/editing_commands_utilities.cc

@@ -615,11 +615,8 @@ void DispatchInputEventEditableContentChanged(
 SelectionInDOMTree CorrectedSelectionAfterCommand(
     const SelectionForUndoStep& passed_selection,
     const Document* document) {
-  if (!passed_selection.Base().IsConnected() ||
-      !passed_selection.Extent().IsConnected() ||
-      passed_selection.Base().GetDocument() != document ||
-      passed_selection.Base().GetDocument() !=
-          passed_selection.Extent().GetDocument())
+  if (!passed_selection.Base().IsValidFor(*document) ||
+      !passed_selection.Extent().IsValidFor(*document))
     return SelectionInDOMTree();
   return passed_selection.AsSelection();
 }

third_party/blink/renderer/core/editing/editor_test.cc

@@ -5,6 +5,7 @@
 #include "third_party/blink/renderer/core/editing/editor.h"
 
 #include "third_party/blink/renderer/core/clipboard/system_clipboard.h"
+#include "third_party/blink/renderer/core/dom/text.h"
 #include "third_party/blink/renderer/core/editing/commands/editor_command.h"
 #include "third_party/blink/renderer/core/editing/frame_selection.h"
 #include "third_party/blink/renderer/core/editing/selection_template.h"
@@ -106,4 +107,19 @@ TEST_F(EditorTest, ReplaceSelection) {
   EXPECT_EQ("HENEWLLO", text_control.value());
 }
 
+// http://crbug.com/873037
+TEST_F(EditorTest, UndoWithInvalidSelection) {
+  const SelectionInDOMTree selection = SetSelectionTextToBody(
+      "<div contenteditable><div></div><b>^abc|</b></div>");
+  Selection().SetSelection(selection, SetSelectionOptions());
+  Text& abc = ToText(*selection.Base().ComputeContainerNode());
+  // Push Text node "abc" into undo stack
+  GetDocument().execCommand("italic", false, "", ASSERT_NO_EXCEPTION);
+  // Change Text node "abc" in undo stack
+  abc.setData("");
+  GetDocument().GetFrame()->GetEditor().Undo();
+  EXPECT_EQ("<div contenteditable><div></div><b>|</b></div>",
+            GetSelectionTextFromBody());
+}
+
 }  // namespace blink