Make "Undo" command to restore selection after validating with the latest Layout tree

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/editing/VisibleSelection.h"
 
 #include "core/dom/Range.h"
 #include "core/editing/EditingTestBase.h"
+#include "core/editing/SelectionAdjuster.h"
 
 #define LOREM_IPSUM \
     "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor " \
     "incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud " \
     "exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure " \
     "dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur." \
     "Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt " \
     "mollit anim id est laborum."
 
 namespace blink {
@@ skipping 324 matching lines @@
         selectionInFlatTree.expandUsingGranularity(WordGranularity);
 
         Range* range = firstRangeOf(selection);
         EXPECT_EQ(0, range->startOffset());
         EXPECT_EQ(11, range->endOffset());
         EXPECT_EQ("Lorem ipsum", range->text());
         testFlatTreePositionsToEqualToDOMTreePositions(selection, selectionInFlatTree);
     }
 }
 
+// This is for crbug.com/627783, simulating restoring selection
+// in undo stack.
+TEST_F(VisibleSelectionTest, validatePositionsIfNeededWithShadowHost)
+{
+    setBodyContent("<div id=host></div><div id=sample>foo</div>");
+    setShadowContent("<content>", "host");
+    Element* sample = document().getElementById("sample");
+
+    // Simulates saving selection in undo stack.
+    VisibleSelection selection(Position(sample->firstChild(), 0));
+    EXPECT_EQ(Position(sample->firstChild(), 0), selection.start());
+
+    // Simulates modifying DOM tree to invalidate distribution.
+    Element* host = document().getElementById("host");
+    host->appendChild(sample);
+
+    // Simulates to restore selection from undo stack.
+    selection.validatePositionsIfNeeded();
+    EXPECT_EQ(Position(sample->firstChild(), 0), selection.start());
+
+    VisibleSelectionInFlatTree selectionInFlatTree;
+    SelectionAdjuster::adjustSelectionInFlatTree(&selectionInFlatTree, selection);
+    EXPECT_EQ(PositionInFlatTree(sample->firstChild(), 0), selectionInFlatTree.start());
+}
+
 } // namespace blink