Introduce VisiblePosition::isValid

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

Index: third_party/WebKit/Source/core/editing/VisiblePositionTest.cpp
diff --git a/third_party/WebKit/Source/core/editing/VisiblePositionTest.cpp b/third_party/WebKit/Source/core/editing/VisiblePositionTest.cpp
index 2b1baab6ed0e4bf2e136f5b2b41d7e6268fd9dc3..d9f21d60b2a9c50ee18c24ca503419049dd39e55 100644
--- a/third_party/WebKit/Source/core/editing/VisiblePositionTest.cpp
+++ b/third_party/WebKit/Source/core/editing/VisiblePositionTest.cpp
@@ -36,4 +36,38 @@ TEST_F(VisiblePositionTest, ShadowV0DistributedNodes)
     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