Introduce composed tree version of nextVisuallyDistinctCandidate()

This patch introduces composed tree version of |nextVisuallyDistinctCandidate()|
by templatizing function to share algorithm.

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

BUG=513568
TEST=webkit_unit_tests --gtest_filter=EditingUtilitiesTest.NextVisuallyDistinctCandidate

Review URL: https://codereview.chromium.org/1317463002

git-svn-id: svn://svn.chromium.org/blink/trunk@201130 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -360,24 +360,35 @@ PositionInComposedTree nextCandidate(const PositionInComposedTree& position)
 // |nextVisuallyDistinctCandidate| is similar to |nextCandidate| except
 // for returning position which |downstream()| not equal to initial position's
 // |downstream()|.
-Position nextVisuallyDistinctCandidate(const Position& position)
+template <typename Strategy>
+static PositionAlgorithm<Strategy> nextVisuallyDistinctCandidateAlgorithm(const PositionAlgorithm<Strategy>& position)
 {
     if (position.isNull())
-        return Position();
+        return PositionAlgorithm<Strategy>();
 
-    PositionIterator p(position);
-    Position downstreamStart = mostForwardCaretPosition(position);
+    PositionIteratorAlgorithm<Strategy> p(position);
+    const PositionAlgorithm<Strategy> downstreamStart = mostForwardCaretPosition(position);
 
     p.increment();
     while (!p.atEnd()) {
-        Position candidate = p.computePosition();
+        PositionAlgorithm<Strategy> candidate = p.computePosition();
         if (isVisuallyEquivalentCandidate(candidate) && mostForwardCaretPosition(candidate) != downstreamStart)
             return candidate;
 
         p.increment();
     }
 
-    return Position();
+    return PositionAlgorithm<Strategy>();
+}
+
+Position nextVisuallyDistinctCandidate(const Position& position)
+{
+    return nextVisuallyDistinctCandidateAlgorithm<EditingStrategy>(position);
+}
+
+PositionInComposedTree nextVisuallyDistinctCandidate(const PositionInComposedTree& position)
+{
+    return nextVisuallyDistinctCandidateAlgorithm<EditingInComposedTreeStrategy>(position);
 }
 
 template <typename Strategy>

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

@@ -162,7 +162,8 @@ PositionInComposedTree nextCandidate(const PositionInComposedTree&);
 Position previousCandidate(const Position&);
 PositionInComposedTree previousCandidate(const PositionInComposedTree&);
 
-Position nextVisuallyDistinctCandidate(const Position&);
+CORE_EXPORT Position nextVisuallyDistinctCandidate(const Position&);
+CORE_EXPORT PositionInComposedTree nextVisuallyDistinctCandidate(const PositionInComposedTree&);
 Position previousVisuallyDistinctCandidate(const Position&);
 PositionInComposedTree previousVisuallyDistinctCandidate(const PositionInComposedTree&);
 

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

@@ -25,4 +25,19 @@ TEST_F(EditingUtilitiesTest, NextNodeIndex)
     EXPECT_EQ(PositionInComposedTree(host, 1), nextPositionOf(PositionInComposedTree(two, 2), PositionMoveType::CodePoint));
 }
 
+TEST_F(EditingUtilitiesTest, NextVisuallyDistinctCandidate)
+{
+    const char* bodyContent = "<p id='host'>00<b id='one'>11</b><b id='two'>22</b><b id='three'>33</b></p>";
+    const char* shadowContent = "<content select=#two></content><content select=#one></content><content select=#three></content>";
+    setBodyContent(bodyContent);
+    setShadowContent(shadowContent);
+    updateLayoutAndStyleForPainting();
+    Node* one = document().getElementById("one");
+    Node* two = document().getElementById("two");
+    Node* three = document().getElementById("three");
+
+    EXPECT_EQ(Position(two->firstChild(), 1), nextVisuallyDistinctCandidate(Position(one, 1)));
+    EXPECT_EQ(PositionInComposedTree(three->firstChild(), 1), nextVisuallyDistinctCandidate(PositionInComposedTree(one, 1)));
+}
+
 } // namespace blink