Add conversion functions for PositionWithAffinity templates

This patch adds ToPositionInDOMTreeWithAffinity() and
ToPositionInFlatTreeWithAffinity() to make PwA conversion easier.

It is also a preparation patch for adding NG line functions.

Change-Id: I4a802a183288fb7a1003ac9cf6e02fe7cad1d4a5
Reviewed-on: https://chromium-review.googlesource.com/1011392Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550531}

third_party/blink/renderer/core/editing/ng_flat_tree_shorthands.cc

@@ -20,9 +20,8 @@ const LayoutBlockFlow* NGInlineFormattingContextOf(
 LocalCaretRect ComputeNGLocalCaretRect(
     const LayoutBlockFlow& context,
     const PositionInFlatTreeWithAffinity& position) {
-  const PositionWithAffinity dom_position(
-      ToPositionInDOMTree(position.GetPosition()), position.Affinity());
-  return ComputeNGLocalCaretRect(context, dom_position);
+  return ComputeNGLocalCaretRect(context,
+                                 ToPositionInDOMTreeWithAffinity(position));
 }
 
 }  // namespace blink

third_party/blink/renderer/core/editing/position_with_affinity.cc

@@ -33,6 +33,28 @@ bool PositionWithAffinityTemplate<Strategy>::operator==(
   return affinity_ == other.affinity_ && position_ == other.position_;
 }
 
+PositionWithAffinity ToPositionInDOMTreeWithAffinity(
+    const PositionWithAffinity& position) {
+  return position;
+}
+
+PositionWithAffinity ToPositionInDOMTreeWithAffinity(
+    const PositionInFlatTreeWithAffinity& position) {
+  return PositionWithAffinity(ToPositionInDOMTree(position.GetPosition()),
+                              position.Affinity());
+}
+
+PositionInFlatTreeWithAffinity ToPositionInFlatTreeWithAffinity(
+    const PositionWithAffinity& position) {
+  return PositionInFlatTreeWithAffinity(
+      ToPositionInFlatTree(position.GetPosition()), position.Affinity());
+}
+
+PositionInFlatTreeWithAffinity ToPositionInFlatTreeWithAffinity(
+    const PositionInFlatTreeWithAffinity& position) {
+  return position;
+}
+
 template class CORE_TEMPLATE_EXPORT
     PositionWithAffinityTemplate<EditingStrategy>;
 template class CORE_TEMPLATE_EXPORT

third_party/blink/renderer/core/editing/position_with_affinity.h

@@ -65,6 +65,15 @@ using PositionWithAffinity = PositionWithAffinityTemplate<EditingStrategy>;
 using PositionInFlatTreeWithAffinity =
     PositionWithAffinityTemplate<EditingInFlatTreeStrategy>;
 
+PositionWithAffinity ToPositionInDOMTreeWithAffinity(
+    const PositionWithAffinity&);
+PositionWithAffinity ToPositionInDOMTreeWithAffinity(
+    const PositionInFlatTreeWithAffinity&);
+PositionInFlatTreeWithAffinity ToPositionInFlatTreeWithAffinity(
+    const PositionWithAffinity&);
+PositionInFlatTreeWithAffinity ToPositionInFlatTreeWithAffinity(
+    const PositionInFlatTreeWithAffinity&);
+
 template <typename Strategy>
 PositionWithAffinityTemplate<Strategy> FromPositionInDOMTree(
     const PositionWithAffinity&);

third_party/blink/renderer/core/editing/visible_units_word.cc

@@ -192,8 +192,7 @@ PositionInFlatTreeWithAffinity NextWordPosition(
 PositionWithAffinity NextWordPosition(const Position& start) {
   const PositionInFlatTreeWithAffinity& next =
       NextWordPosition(ToPositionInFlatTree(start));
-  return PositionWithAffinity(ToPositionInDOMTree(next.GetPosition()),
-                              next.Affinity());
+  return ToPositionInDOMTreeWithAffinity(next);
 }
 
 // TODO(yosin): This function will be removed by replacing call sites to use