Introduce visiblePositionOf() for Position and PositionInComposedTree

Source/core/editing/VisiblePositionTest.cpp

Index: Source/core/editing/VisiblePositionTest.cpp
diff --git a/Source/core/editing/VisiblePositionTest.cpp b/Source/core/editing/VisiblePositionTest.cpp
index f8759045cb9e1075b3e6f224ef47c530e0b4d6b7..4a18307e76b358a81bcc7e1046a740bbede7db3d 100644
--- a/Source/core/editing/VisiblePositionTest.cpp
+++ b/Source/core/editing/VisiblePositionTest.cpp
@@ -31,9 +31,9 @@ TEST_F(VisiblePositionTest, ShadowDistributedNodes)
     EXPECT_EQ(Position(one->firstChild(), 2), VisiblePosition(Position(two.get(), 0)).deepEquivalent());
 
     EXPECT_EQ(PositionInComposedTree(five->firstChild(), 2), canonicalPositionOf(PositionInComposedTree(one.get(), 0)));
-    EXPECT_EQ(Position(five->firstChild(), 2), VisiblePosition(PositionInComposedTree(one.get(), 0)).deepEquivalent());
+    EXPECT_EQ(Position(five->firstChild(), 2), visiblePositionOf(PositionInComposedTree(one.get(), 0)).deepEquivalent());
     EXPECT_EQ(PositionInComposedTree(four->firstChild(), 2), canonicalPositionOf(PositionInComposedTree(two.get(), 0)));
-    EXPECT_EQ(Position(four->firstChild(), 2), VisiblePosition(PositionInComposedTree(two.get(), 0)).deepEquivalent());
+    EXPECT_EQ(Position(four->firstChild(), 2), visiblePositionOf(PositionInComposedTree(two.get(), 0)).deepEquivalent());
 }
 
 } // namespace blink