Add DocumentMarkerList in preparation for DocumentMarkerController refactor

third_party/WebKit/Source/core/editing/markers/DocumentMarker.cpp

Index: third_party/WebKit/Source/core/editing/markers/DocumentMarker.cpp
diff --git a/third_party/WebKit/Source/core/editing/markers/DocumentMarker.cpp b/third_party/WebKit/Source/core/editing/markers/DocumentMarker.cpp
index b18b3fd88304206850783d3ee5de7a20483edd5f..7465262ac7324e34a6102a1154e37cefc431b5c4 100644
--- a/third_party/WebKit/Source/core/editing/markers/DocumentMarker.cpp
+++ b/third_party/WebKit/Source/core/editing/markers/DocumentMarker.cpp
@@ -166,6 +166,53 @@ DocumentMarker::DocumentMarker(const DocumentMarker& marker)
       m_endOffset(marker.endOffset()),
       m_details(marker.details()) {}
 
+DocumentMarker::ShiftMarkerResult DocumentMarker::getShiftedMarkerPosition(

[Xiaocheng, 2017/03/29 19:41:43]

nit: I think the previous patch should directly implement this function in
DocumentMarker, so that we don't need to move it in this patch.

It also makes it easy to compare the behavior change.

+    unsigned offset,
+    unsigned oldLength,
+    unsigned newLength) const {
+  ShiftMarkerResult result;
+  result.newStartOffset = startOffset();
+  result.newEndOffset = endOffset();
+  result.shouldRemoveMarker = false;
+
+  // algorithm inspired by https://dom.spec.whatwg.org/#concept-cd-replace
+  // but with some changes
+
+  // Deviation from the concept-cd-replace algorithm: second condition in the
+  // next line (don't include text inserted immediately before a marker in the
+  // marked range, but do include the new text if it's replacing text in the
+  // marked range)
+  if (startOffset() > offset || (startOffset() == offset && oldLength == 0)) {
+    if (startOffset() <= offset + oldLength) {
+      // Marker start was in the replaced text. Move to end of new text
+      // (Deviation from the concept-cd-replace algorithm: that algorithm
+      // would move to the beginning of the new text here)
+      result.newStartOffset = offset + newLength;
+    } else {
+      // Marker start was after the replaced text. Shift by length
+      // difference
+      result.newStartOffset = startOffset() + newLength - oldLength;
+    }
+  }
+
+  if (endOffset() > offset) {
+    // Deviation from the concept-cd-replace algorithm: < instead of <= in
+    // the next line
+    if (endOffset() < offset + oldLength) {
+      // Marker end was in the replaced text. Move to beginning of new text
+      result.newEndOffset = offset;
+    } else {
+      // Marker end was after the replaced text. Shift by length difference
+      result.newEndOffset = endOffset() + newLength - oldLength;
+    }
+  }
+
+  if (result.newStartOffset >= result.newEndOffset)
+    result.shouldRemoveMarker = true;
+
+  return result;
+}
+
 void DocumentMarker::shiftOffsets(int delta) {
   m_startOffset += delta;
   m_endOffset += delta;