Revert "Stop ExpandRange/EndToSentenceBoundary from using VisiblePosition"

This reverts commit 390c941f.

Reason for revert: causing layout test failure crbug.com/906174

Original change's description:
> Stop ExpandRange/EndToSentenceBoundary from using VisiblePosition
> 
> This patch stops the two functions from using VisiblePosition by switch
> to the VP-free versions of Start/EndOfSentence(). Hence, this patch
> reduces the usage of legacy VisiblePosition.
> 
> Bug: 657237
> Change-Id: I933a020f9bd6643ba1b2cd5111b8be18b2f49086
> Reviewed-on: https://chromium-review.googlesource.com/c/1337816
> Reviewed-by: Yoichi Osato <yoichio@chromium.org>
> Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
> Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#608849}

TBR=yosin@chromium.org,yoichio@chromium.org,xiaochengh@chromium.org

Bug: 657237, 906174
Change-Id: I915e9d68f16a11344b0160db4c5702113380273a
Reviewed-on: https://chromium-review.googlesource.com/c/1340899
Commit-Queue: Ella Ge <eirage@chromium.org>
Reviewed-by: Ella Ge <eirage@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608963}

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

@@ -138,9 +138,6 @@ CORE_EXPORT PositionWithAffinity PreviousWordPosition(const Position&);
 CORE_EXPORT PositionWithAffinity NextWordPosition(const Position&);
 
 // sentences
-CORE_EXPORT Position StartOfSentencePosition(const Position&);
-CORE_EXPORT PositionInFlatTree
-StartOfSentencePosition(const PositionInFlatTree&);
 CORE_EXPORT VisiblePosition StartOfSentence(const VisiblePosition&);
 CORE_EXPORT VisiblePositionInFlatTree
 StartOfSentence(const VisiblePositionInFlatTree&);

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

@@ -196,8 +196,10 @@ VisiblePositionInFlatTree EndOfSentence(const VisiblePositionInFlatTree& c) {
 
 EphemeralRange ExpandEndToSentenceBoundary(const EphemeralRange& range) {
   DCHECK(range.IsNotNull());
-  const Position& sentence_end =
-      EndOfSentence(range.EndPosition()).GetPosition();
+  const VisiblePosition& visible_end =
+      CreateVisiblePosition(range.EndPosition());
+  DCHECK(visible_end.IsNotNull());
+  const Position& sentence_end = EndOfSentence(visible_end).DeepEquivalent();
   // TODO(editing-dev): |sentenceEnd < range.endPosition()| is possible,
   // which would trigger a DCHECK in EphemeralRange's constructor if we return
   // it directly. However, this shouldn't happen and needs to be fixed.
@@ -210,8 +212,11 @@ EphemeralRange ExpandEndToSentenceBoundary(const EphemeralRange& range) {
 
 EphemeralRange ExpandRangeToSentenceBoundary(const EphemeralRange& range) {
   DCHECK(range.IsNotNull());
+  const VisiblePosition& visible_start =
+      CreateVisiblePosition(range.StartPosition());
+  DCHECK(visible_start.IsNotNull());
   const Position& sentence_start =
-      StartOfSentencePosition(range.StartPosition());
+      StartOfSentence(visible_start).DeepEquivalent();
   // TODO(editing-dev): |sentenceStart > range.startPosition()| is possible,
   // which would trigger a DCHECK in EphemeralRange's constructor if we return
   // it directly. However, this shouldn't happen and needs to be fixed.