Introduce composed tree version of firstEditableVisiblePositionAfterPositionInRoot()

Source/core/editing/EditingUtilitiesTest.cpp

Index: Source/core/editing/EditingUtilitiesTest.cpp
diff --git a/Source/core/editing/EditingUtilitiesTest.cpp b/Source/core/editing/EditingUtilitiesTest.cpp
index cc7f02fd136dfb0f259855d1a87d3cfbc06573a3..3775dcb560c07fff64afc43af3bf7a8ecb042d95 100644
--- a/Source/core/editing/EditingUtilitiesTest.cpp
+++ b/Source/core/editing/EditingUtilitiesTest.cpp
@@ -27,21 +27,26 @@ TEST_F(EditingUtilitiesTest, directionOfEnclosingBlock)
 
 TEST_F(EditingUtilitiesTest, firstEditablePositionAfterPositionInRoot)
 {
-    const char* bodyContent = "<p id='host' contenteditable><b id='one'></b><b id='two'>22</b></p>";
+    const char* bodyContent = "<p id='host' contenteditable><b id='one'>1</b><b id='two'>22</b></p>";
     const char* shadowContent = "<content select=#two></content><content select=#one></content><b id='three'>333</b>";
     setBodyContent(bodyContent);
     RefPtrWillBeRawPtr<ShadowRoot> shadowRoot = setShadowContent(shadowContent, "host");
     updateLayoutAndStyleForPainting();
-    Node* host = document().getElementById("host");
+    Element* host = document().getElementById("host");
     Node* one = document().getElementById("one");
+    Node* two = document().getElementById("two");
     Node* three = shadowRoot->getElementById("three");
 
     EXPECT_EQ(Position(one, 0), firstEditablePositionAfterPositionInRoot(Position(one, 0), host));
+    EXPECT_EQ(Position(one->firstChild(), 0), firstEditableVisiblePositionAfterPositionInRoot(Position(one, 0), host).deepEquivalent());
 
     EXPECT_EQ(PositionInComposedTree(one, 0), firstEditablePositionAfterPositionInRoot(PositionInComposedTree(one, 0), host));
+    EXPECT_EQ(PositionInComposedTree(two->firstChild(), 2), firstEditableVisiblePositionAfterPositionInRoot(PositionInComposedTree(one, 0), host).deepEquivalent());
 
     EXPECT_EQ(Position::firstPositionInNode(host), firstEditablePositionAfterPositionInRoot(Position(three, 0), host));
+    EXPECT_EQ(Position(one->firstChild(), 0), firstEditableVisiblePositionAfterPositionInRoot(Position(three, 0), host).deepEquivalent());
     EXPECT_EQ(PositionInComposedTree::afterNode(host), firstEditablePositionAfterPositionInRoot(PositionInComposedTree(three, 0), host));
+    EXPECT_EQ(PositionInComposedTree::lastPositionInNode(host), firstEditableVisiblePositionAfterPositionInRoot(PositionInComposedTree(three, 0), host).deepEquivalent());
 }
 
 TEST_F(EditingUtilitiesTest, enclosingBlock)