Make CalcSelection return EphemeralRange.

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

Index: third_party/WebKit/Source/core/editing/LayoutSelection.cpp
diff --git a/third_party/WebKit/Source/core/editing/LayoutSelection.cpp b/third_party/WebKit/Source/core/editing/LayoutSelection.cpp
index 8d87696471ccc12588e00077d133d8478233925b..3f74aa4de251f8af20bf3bc278b0087739a690a3 100644
--- a/third_party/WebKit/Source/core/editing/LayoutSelection.cpp
+++ b/third_party/WebKit/Source/core/editing/LayoutSelection.cpp
@@ -120,20 +120,21 @@ static bool ShouldShowBlockCursor(const FrameSelection& frame_selection,
   return true;
 }
 
-static VisibleSelectionInFlatTree CalcSelection(
+static std::pair<PositionInFlatTree, PositionInFlatTree> CalcSelection(

[yosin_UTC9, 2017/07/04 05:56:41]

Let's use |EphemeralRangeInFlatTree()| rather than
|std::pair<PositionInFlatTree, PositionInFlatTree>|
to utilize existing class and this pair holds first <= second and this pair
should be first.IsNull() when second.IsNull().

[yoichio, 2017/07/04 06:31:30]

I will introduce a class kind of pair<LayoutObject, int>. It may hold
 LayoutObject w/o Node like  list-style-image.

[yosin_UTC9, 2017/07/04 07:28:43]

We may want to introduce SelectionRange instead of std::pair<SelectionPosition,
Position>,
although |SelectionPositon| and |SelectionRange| aren't good names.

std:pair<a, b> is a kind of anonymous struct, we want to access members with
meaningful name
e.g. start/end instead of first/second.

Since we want to reduce usage of VisibleSelection, crbug.com/657237, it is good
idea to
return |EphemeralRange| instead of |VisibleSeleciton| instead of a preparation
of
crrev.com/2962143002/

[yoichio, 2017/07/04 08:02:45]

Intorducd |using SelectionRange = std::pair<PositionInFlatTree,
PositionInFlatTree>|.

     const FrameSelection& frame_selection) {
   const VisibleSelectionInFlatTree& original_selection =
       frame_selection.ComputeVisibleSelectionInFlatTree();
 
   if (!ShouldShowBlockCursor(frame_selection, original_selection))
-    return original_selection;
+    return {original_selection.Start(), original_selection.End()};
 
   const PositionInFlatTree end_position = NextPositionOf(
       original_selection.Start(), PositionMoveType::kGraphemeCluster);
-  return CreateVisibleSelection(
+  const VisibleSelectionInFlatTree& block_cursor = CreateVisibleSelection(
       SelectionInFlatTree::Builder()
           .SetBaseAndExtent(original_selection.Start(), end_position)
           .Build());
+  return {block_cursor.Start(), block_cursor.End()};
 }
 
 // Objects each have a single selection rect to examine.
@@ -297,13 +298,13 @@ static SelectionPaintRange CalcSelectionPaintRange(
   if (selection_in_dom.IsNone())
     return SelectionPaintRange();
 
-  const VisibleSelectionInFlatTree& selection = CalcSelection(frame_selection);
-  if (!selection.IsRange() || frame_selection.IsHidden())
+  const auto& selection = CalcSelection(frame_selection);
+  if ((selection.first.IsNull() || selection.first == selection.second) ||
+      frame_selection.IsHidden())
     return SelectionPaintRange();
 
-  DCHECK(!selection.IsNone());
-  const PositionInFlatTree start_pos = selection.Start();
-  const PositionInFlatTree end_pos = selection.End();
+  const PositionInFlatTree start_pos = selection.first;
+  const PositionInFlatTree end_pos = selection.second;
   DCHECK_LE(start_pos, end_pos);
   LayoutObject* start_layout_object = start_pos.AnchorNode()->GetLayoutObject();
   LayoutObject* end_layout_object = end_pos.AnchorNode()->GetLayoutObject();