Introduce VisiblePosition::isValid

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

 // Copyright 2015 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/VisiblePosition.h"
 
 #include "core/editing/EditingTestBase.h"
 #include "core/editing/VisibleUnits.h"
 
 namespace blink {
@@ skipping 18 matching lines @@
     EXPECT_EQ(Position(one->firstChild(), 0), createVisiblePosition(Position(one, 0)).deepEquivalent());
     EXPECT_EQ(Position(one->firstChild(), 2), canonicalPositionOf(Position(two, 0)));
     EXPECT_EQ(Position(one->firstChild(), 2), createVisiblePosition(Position(two, 0)).deepEquivalent());
 
     EXPECT_EQ(PositionInFlatTree(five->firstChild(), 2), canonicalPositionOf(PositionInFlatTree(one, 0)));
     EXPECT_EQ(PositionInFlatTree(five->firstChild(), 2), createVisiblePosition(PositionInFlatTree(one, 0)).deepEquivalent());
     EXPECT_EQ(PositionInFlatTree(four->firstChild(), 2), canonicalPositionOf(PositionInFlatTree(two, 0)));
     EXPECT_EQ(PositionInFlatTree(four->firstChild(), 2), createVisiblePosition(PositionInFlatTree(two, 0)).deepEquivalent());
 }
 
+#if DCHECK_IS_ON()
+
+TEST_F(VisiblePositionTest, NullIsValid)
+{
+    EXPECT_TRUE(VisiblePosition().isValid());
+}
+
+TEST_F(VisiblePositionTest, NonNullIsValidInCleanTree)
+{
+    setBodyContent("<p>one</p>");
+
+    Element* paragraph = document().querySelector("p");
+    Position position(paragraph->firstChild(), 1);
+    EXPECT_TRUE(createVisiblePosition(position).isValid());
+}
+
+TEST_F(VisiblePositionTest, NonNullInvalidatedAfterMutation)
+{
+    setBodyContent("<p>one</p>");
+
+    Element* paragraph = document().querySelector("p");
+    Position position(paragraph->firstChild(), 1);
+    VisiblePosition nullVisiblePosition;
+    VisiblePosition nonNullVisiblePosition = createVisiblePosition(position);
+
+    Element* div = document().createElement("div", ASSERT_NO_EXCEPTION);
+    document().body()->appendChild(div);
+
+    EXPECT_TRUE(nullVisiblePosition.isValid());
+    EXPECT_FALSE(nonNullVisiblePosition.isValid());
+}
+
+#endif

[yosin_UTC9, 2016/09/20 13:55:51]

Let's check "display" property change.
Not sure about "color", is changing "color" turns
|Document::needsLayoutTreeUpdare()| to true?

[Xiaocheng, 2016/09/21 06:31:49]

Done.

+
 } // namespace blink