Introduce composed tree version of startOfDocument()

This patch introduces composed tree version of |startOfDocument()| by
templatizing original |startOfDocument()| to work both DOM tree position and
composed tree position version for introducing composed tree version of
|VisibleSelection| class.

This patch is a preparation of making selection to handle granularity for web
component, http://crrev.com/1277863002

BUG=513568
TEST=n/a; no behavior changes

Review URL: https://codereview.chromium.org/1324123003

git-svn-id: svn://svn.chromium.org/blink/trunk@201979 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -1557,17 +1557,24 @@ bool isEndOfBlock(const VisiblePosition& pos)
 
 // ---------
 
-VisiblePosition startOfDocument(const Node* node)
+template <typename Strategy>
+static VisiblePositionTemplate<Strategy> startOfDocumentAlgorithm(const VisiblePositionTemplate<Strategy>& visiblePosition)
 {
+    Node* node = visiblePosition.deepEquivalent().anchorNode();
     if (!node || !node->document().documentElement())
-        return VisiblePosition();
+        return VisiblePositionTemplate<Strategy>();
 
-    return createVisiblePosition(firstPositionInNode(node->document().documentElement()));
+    return createVisiblePosition(PositionAlgorithm<Strategy>::firstPositionInNode(node->document().documentElement()));
 }
 
 VisiblePosition startOfDocument(const VisiblePosition& c)
 {
-    return startOfDocument(c.deepEquivalent().anchorNode());
+    return startOfDocumentAlgorithm<EditingStrategy>(c);
+}
+
+VisiblePositionInComposedTree startOfDocument(const VisiblePositionInComposedTree& c)
+{
+    return startOfDocumentAlgorithm<EditingInComposedTreeStrategy>(c);
 }
 
 template <typename Strategy>

third_party/WebKit/Source/core/editing/VisibleUnits.h

@@ -162,8 +162,8 @@ bool isStartOfBlock(const VisiblePosition&);
 bool isEndOfBlock(const VisiblePosition&);
 
 // document
-VisiblePosition startOfDocument(const Node*);
-VisiblePosition startOfDocument(const VisiblePosition&);
+CORE_EXPORT VisiblePosition startOfDocument(const VisiblePosition&);
+CORE_EXPORT VisiblePositionInComposedTree startOfDocument(const VisiblePositionInComposedTree&);
 CORE_EXPORT VisiblePosition endOfDocument(const VisiblePosition&);
 CORE_EXPORT VisiblePositionInComposedTree endOfDocument(const VisiblePositionInComposedTree&);
 bool isStartOfDocument(const VisiblePosition&);

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

@@ -359,4 +359,22 @@ TEST_F(VisibleUnitsTest, rightPositionOf)
     EXPECT_EQ(PositionInComposedTree(three, 0), rightPositionOf(createVisiblePosition(PositionInComposedTree(five, 5))).deepEquivalent());
 }
 
+TEST_F(VisibleUnitsTest, startOfDocument)
+{
+    const char* bodyContent = "<a id=host><b id=one>1</b><b id=two>22</b></a>";
+    const char* shadowContent = "<p><content select=#two></content></p><p><content select=#one></content></p>";
+    setBodyContent(bodyContent);
+    setShadowContent(shadowContent, "host");
+    updateLayoutAndStyleForPainting();
+
+    Node* one = document().getElementById("one")->firstChild();
+    Node* two = document().getElementById("two")->firstChild();
+
+    EXPECT_EQ(Position(one, 0), startOfDocument(createVisiblePositionInDOMTree(*one, 0)).deepEquivalent());
+    EXPECT_EQ(PositionInComposedTree(two, 0), startOfDocument(createVisiblePositionInComposedTree(*one, 0)).deepEquivalent());
+
+    EXPECT_EQ(Position(one, 0), startOfDocument(createVisiblePositionInDOMTree(*two, 1)).deepEquivalent());
+    EXPECT_EQ(PositionInComposedTree(two, 0), startOfDocument(createVisiblePositionInComposedTree(*two, 1)).deepEquivalent());
+}
+
 } // namespace blink