Introduce ComposedTreeTraversal::previousPostOrder()

Source/core/dom/shadow/ComposedTreeTraversalTest.cpp

Index: Source/core/dom/shadow/ComposedTreeTraversalTest.cpp
diff --git a/Source/core/dom/shadow/ComposedTreeTraversalTest.cpp b/Source/core/dom/shadow/ComposedTreeTraversalTest.cpp
index 346e39dafafe5115c81caefac94ab3efe2c098f6..f653c7e3856362360150e652e0e1c11edd498012 100644
--- a/Source/core/dom/shadow/ComposedTreeTraversalTest.cpp
+++ b/Source/core/dom/shadow/ComposedTreeTraversalTest.cpp
@@ -324,4 +324,52 @@ TEST_F(ComposedTreeTraversalTest, lastWithin)
     EXPECT_EQ(*m10->firstChild(), ComposedTreeTraversal::lastWithinOrSelf(*s12));
 }
 
+TEST_F(ComposedTreeTraversalTest, previousPostOrder)
+{
+    const char* mainHTML =
+        "<div id='m0'>m0</div>"
+        "<div id='m1'>"
+            "<span id='m10'>m10</span>"
+            "<span id='m11'>m11</span>"
+        "</div>"
+        "<div id='m2'>m2</div>";
+    const char* shadowHTML =
+        "<content select='#m11'></content>"
+        "<a id='s11'>s11</a>"
+        "<a id='s12'>"
+            "<b id='s120'>s120</b>"
+            "<content select='#m10'></content>"
+        "</a>";
+    setupSampleHTML(mainHTML, shadowHTML, 1);
+
+    RefPtrWillBeRawPtr<Element> body = document().body();
+    RefPtrWillBeRawPtr<Element> m0 = body->querySelector("#m0", ASSERT_NO_EXCEPTION);
+    RefPtrWillBeRawPtr<Element> m1 = body->querySelector("#m1", ASSERT_NO_EXCEPTION);
+    RefPtrWillBeRawPtr<Element> m2 = body->querySelector("#m2", ASSERT_NO_EXCEPTION);
+
+    RefPtrWillBeRawPtr<Element> m10 = body->querySelector("#m10", ASSERT_NO_EXCEPTION);
+    RefPtrWillBeRawPtr<Element> m11 = body->querySelector("#m11", ASSERT_NO_EXCEPTION);
+
+    RefPtrWillBeRawPtr<ShadowRoot> shadowRoot = m1->openShadowRoot();
+    RefPtrWillBeRawPtr<Element> s11 = shadowRoot->querySelector("#s11", ASSERT_NO_EXCEPTION);
+    RefPtrWillBeRawPtr<Element> s12 = shadowRoot->querySelector("#s12", ASSERT_NO_EXCEPTION);
+    RefPtrWillBeRawPtr<Element> s120 = shadowRoot->querySelector("#s120", ASSERT_NO_EXCEPTION);
+
+    EXPECT_EQ(*m0->firstChild(), ComposedTreeTraversal::previousPostOrder(*m0));
+    EXPECT_EQ(*s12, ComposedTreeTraversal::previousPostOrder(*m1));
+    EXPECT_EQ(*m10->firstChild(), ComposedTreeTraversal::previousPostOrder(*m10));
+    EXPECT_EQ(*s120, ComposedTreeTraversal::previousPostOrder(*m10->firstChild()));
+    EXPECT_EQ(*s120, ComposedTreeTraversal::previousPostOrder(*m10->firstChild(), s12.get()));
+    EXPECT_EQ(*m11->firstChild(), ComposedTreeTraversal::previousPostOrder(*m11));
+    EXPECT_EQ(*m0, ComposedTreeTraversal::previousPostOrder(*m11->firstChild()));
+    EXPECT_EQ(nullptr, ComposedTreeTraversal::previousPostOrder(*m11->firstChild(), m11.get()));
+    EXPECT_EQ(*m2->firstChild(), ComposedTreeTraversal::previousPostOrder(*m2));
+
+    EXPECT_EQ(*s11->firstChild(), ComposedTreeTraversal::previousPostOrder(*s11));
+    EXPECT_EQ(*m10, ComposedTreeTraversal::previousPostOrder(*s12));
+    EXPECT_EQ(*s120->firstChild(), ComposedTreeTraversal::previousPostOrder(*s120));
+    EXPECT_EQ(*s11, ComposedTreeTraversal::previousPostOrder(*s120->firstChild()));
+    EXPECT_EQ(nullptr, ComposedTreeTraversal::previousPostOrder(*s120->firstChild(), s12.get()));
+}
+
 } // namespace blink