Introduce LayoutSelection::SelectionStart()/End() to TouchAdjustment.

Since integers returned by SelectionStartEnd() don't relate 
each other if start LayoutObject != end LayoutObject.
To emphasize that for readability, we should split it.

Bug: 739062
Change-Id: I9609262fe2aeb63a49fa95a4d17de66c167d92f8
Reviewed-on: https://chromium-review.googlesource.com/566268
Commit-Queue: Yoichi Osato <yoichio@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486695}

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

@@ -1163,6 +1163,13 @@ std::pair<int, int> FrameSelection::LayoutSelectionStartEnd() {
   return layout_selection_->SelectionStartEnd();
 }
 
+base::Optional<int> FrameSelection::LayoutSelectionStart() const {
+  return layout_selection_->SelectionStart();
+}
+base::Optional<int> FrameSelection::LayoutSelectionEnd() const {
+  return layout_selection_->SelectionEnd();
+}
+
 void FrameSelection::ClearLayoutSelection() {
   layout_selection_->ClearSelection();
 }

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

@@ -244,6 +244,8 @@ class CORE_EXPORT FrameSelection final
   FrameCaret& FrameCaretForTesting() const { return *frame_caret_; }
 
   std::pair<int, int> LayoutSelectionStartEnd();
+  base::Optional<int> LayoutSelectionStart() const;
+  base::Optional<int> LayoutSelectionEnd() const;
   void ClearLayoutSelection();
 
   DECLARE_TRACE();

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

@@ -297,6 +297,20 @@ std::pair<int, int> LayoutSelection::SelectionStartEnd() {
   return std::make_pair(paint_range_.StartOffset(), paint_range_.EndOffset());
 }
 
+base::Optional<int> LayoutSelection::SelectionStart() const {
+  DCHECK(!HasPendingSelection());
+  if (paint_range_.IsNull())
+    return {};
+  return paint_range_.StartOffset();
+}
+
+base::Optional<int> LayoutSelection::SelectionEnd() const {
+  DCHECK(!HasPendingSelection());
+  if (paint_range_.IsNull())
+    return {};
+  return paint_range_.EndOffset();
+}
+
 void LayoutSelection::ClearSelection() {
   // For querying Layer::compositingState()
   // This is correct, since destroying layout objects needs to cause eager paint

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

@@ -100,7 +100,10 @@ class LayoutSelection final : public GarbageCollected<LayoutSelection> {
   void InvalidatePaintForSelection();
 
   void ClearSelection();
+  // TODO(yoiciho): Replace SelectionStartEnd with SelectionStart/End.
   std::pair<int, int> SelectionStartEnd();
+  base::Optional<int> SelectionStart() const;
+  base::Optional<int> SelectionEnd() const;
   void OnDocumentShutdown();
 
   DECLARE_TRACE();

third_party/WebKit/Source/core/page/TouchAdjustment.cpp

@@ -204,6 +204,8 @@ static inline void AppendContextSubtargetsForNode(
   } else {
     if (text_layout_object->GetSelectionState() == SelectionState::kNone)
       return AppendBasicSubtargetsForNode(node, subtargets);
+    const FrameSelection& frame_selection =
+        text_layout_object->GetFrame()->Selection();
     // If selected, make subtargets out of only the selected part of the text.
     int start_pos, end_pos;
     switch (text_layout_object->GetSelectionState()) {
@@ -212,15 +214,16 @@ static inline void AppendContextSubtargetsForNode(
         end_pos = text_layout_object->TextLength();
         break;
       case SelectionState::kStart:
-        std::tie(start_pos, end_pos) = text_layout_object->SelectionStartEnd();
+        start_pos = frame_selection.LayoutSelectionStart().value();
         end_pos = text_layout_object->TextLength();
         break;
       case SelectionState::kEnd:
-        std::tie(start_pos, end_pos) = text_layout_object->SelectionStartEnd();
         start_pos = 0;
+        end_pos = frame_selection.LayoutSelectionEnd().value();
         break;
       case SelectionState::kStartAndEnd:
-        std::tie(start_pos, end_pos) = text_layout_object->SelectionStartEnd();
+        start_pos = frame_selection.LayoutSelectionStart().value();
+        end_pos = frame_selection.LayoutSelectionEnd().value();
         break;
       default:
         NOTREACHED();