[LayoutNG] Convert GetMappingUnitsForDOMOffsetRange to take EphemeralRange

This patch changes the API to take Position parameters to better support
mapping non-text anchored positions to LayoutNG canonical text.

After this patch, NGOffsetMapping is fully converted to take Position parameters.

Bug: 699017
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Iee9956dc59c1ab34fe03f9f0f11fe890ddf9e568
Reviewed-on: https://chromium-review.googlesource.com/744733
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513010}

third_party/WebKit/Source/core/editing/iterators/TextIteratorTextNodeHandler.cpp

@@ -6,6 +6,7 @@
 
 #include <algorithm>
 #include "core/dom/FirstLetterPseudoElement.h"
+#include "core/editing/EphemeralRange.h"
 #include "core/editing/iterators/TextIteratorTextState.h"
 #include "core/layout/LayoutTextFragment.h"
 #include "core/layout/line/InlineTextBox.h"
@@ -91,9 +92,12 @@ void TextIteratorTextNodeHandler::HandleTextNodeWithLayoutNG() {
   }
 
   while (offset_ < end_offset_ && !text_state_.PositionNode()) {
+    const EphemeralRange range_to_emit(Position(text_node_, offset_),
+                                       Position(text_node_, end_offset_));
+
     // We may go through multiple mappings, which happens when there is
     // ::first-letter and blockifying style.
-    auto* mapping = NGOffsetMapping::GetFor(Position(text_node_, offset_));
+    auto* mapping = NGOffsetMapping::GetFor(range_to_emit.StartPosition());
     if (!mapping) {
       offset_ = end_offset_;
       return;
@@ -101,8 +105,7 @@ void TextIteratorTextNodeHandler::HandleTextNodeWithLayoutNG() {
 
     const unsigned initial_offset = offset_;
     for (const NGOffsetMappingUnit& unit :
-         mapping->GetMappingUnitsForDOMOffsetRange(*text_node_, offset_,
-                                                   end_offset_)) {
+         mapping->GetMappingUnitsForDOMRange(range_to_emit)) {
       const unsigned run_start = std::max(offset_, unit.DOMStart());
       const unsigned run_end = std::min(end_offset_, unit.DOMEnd());
       if (run_start >= run_end ||

third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping.cc

@@ -6,6 +6,7 @@
 
 #include "core/dom/Node.h"
 #include "core/dom/Text.h"
+#include "core/editing/EphemeralRange.h"
 #include "core/editing/Position.h"
 #include "core/layout/ng/inline/ng_inline_node.h"
 
@@ -176,10 +177,15 @@ const NGOffsetMappingUnit* NGOffsetMapping::GetMappingUnitForPosition(
   return unit;
 }
 
-NGMappingUnitRange NGOffsetMapping::GetMappingUnitsForDOMOffsetRange(
-    const Node& node,
-    unsigned start_offset,
-    unsigned end_offset) const {
+NGMappingUnitRange NGOffsetMapping::GetMappingUnitsForDOMRange(
+    const EphemeralRange& range) const {
+  DCHECK(NGOffsetMapping::AcceptsPosition(range.StartPosition()));
+  DCHECK(NGOffsetMapping::AcceptsPosition(range.EndPosition()));
+  DCHECK_EQ(range.StartPosition().AnchorNode(),
+            range.EndPosition().AnchorNode());
+  const Node& node = *range.StartPosition().AnchorNode();
+  const unsigned start_offset = ToNodeOffsetPair(range.StartPosition()).second;
+  const unsigned end_offset = ToNodeOffsetPair(range.EndPosition()).second;
   unsigned range_start;
   unsigned range_end;
   std::tie(range_start, range_end) = ranges_.at(&node);

third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping.h

@@ -106,9 +106,6 @@ class CORE_EXPORT NGOffsetMapping {
 
   // ------ Mapping APIs from DOM to text content ------
 
-  // TODO(xiaochengh): Change the functions to take Positions instead of (node,
-  // offset) pairs.
-
   // Note: any Position passed to the APIs must be in either of the two types:
   // 1. Offset-in-anchor in text node
   // 2. Before/After-anchor of BR or atomic inline
@@ -128,10 +125,9 @@ class CORE_EXPORT NGOffsetMapping {
   const NGOffsetMappingUnit* GetMappingUnitForPosition(const Position&) const;
 
   // Returns all NGOffsetMappingUnits whose DOM ranges has non-empty (but
-  // possibly collapsed) intersections with the passed in DOM offset range.
-  NGMappingUnitRange GetMappingUnitsForDOMOffsetRange(const Node&,
-                                                      unsigned,
-                                                      unsigned) const;
+  // possibly collapsed) intersections with the passed in DOM range. This API
+  // only accepts ranges whose start and end have the same anchor node.
+  NGMappingUnitRange GetMappingUnitsForDOMRange(const EphemeralRange&) const;
 
   // Returns the text content offset corresponding to the given position.
   // Returns nullopt when the position is not laid out in this block.