Make StartOfDocument() to take/return Position

This patch changes |StartOfDocument()| to take/return |Position| instead
of |VisiblePosition| to reduce usage of |VisiblePosition|.

Note: This patch doesn't change behavior.

Bug: 657237
Change-Id: I3832f42b8c08b63dee92a390945e7993f92bcc71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2567843
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832707}

third_party/blink/renderer/core/dom/range.cc

@@ -1597,7 +1597,7 @@ void Range::expand(const String& unit, ExceptionState& exception_state) {
     start = StartOfParagraph(start);
     end = EndOfParagraph(end);
   } else if (unit == "document") {
-    start = StartOfDocument(start);
+    start = CreateVisiblePosition(StartOfDocument(start.DeepEquivalent()));
     end = EndOfDocument(end);
   } else {
     return;

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

@@ -143,7 +143,8 @@ class GranularityAdjuster final {
         return StartOfParagraph(pos).DeepEquivalent();
       }
       case TextGranularity::kDocumentBoundary:
-        return StartOfDocument(CreateVisiblePosition(passed_start))
+        return CreateVisiblePosition(
+                   StartOfDocument(passed_start.GetPosition()))
             .DeepEquivalent();
       case TextGranularity::kParagraphBoundary:
         return StartOfParagraph(CreateVisiblePosition(passed_start))

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

@@ -601,7 +601,7 @@ VisiblePosition SelectionModifier::ModifyExtendingBackwardInternal(
         return CreateVisiblePosition(
             StartOfEditableContent(pos.DeepEquivalent()));
       }
-      return StartOfDocument(pos);
+      return CreateVisiblePosition(StartOfDocument(pos.DeepEquivalent()));
     }
   }
   NOTREACHED() << static_cast<int>(granularity);
@@ -697,7 +697,7 @@ VisiblePosition SelectionModifier::ModifyMovingBackward(
         pos =
             CreateVisiblePosition(StartOfEditableContent(pos.DeepEquivalent()));
       } else {
-        pos = StartOfDocument(pos);
+        pos = CreateVisiblePosition(StartOfDocument(pos.DeepEquivalent()));
       }
       break;
   }

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

@@ -357,22 +357,21 @@ static Node* ParentEditingBoundary(const PositionTemplate<Strategy>& position) {
 // ---------
 
 template <typename Strategy>
-static VisiblePositionTemplate<Strategy> StartOfDocumentAlgorithm(
-    const VisiblePositionTemplate<Strategy>& visible_position) {
-  DCHECK(visible_position.IsValid()) << visible_position;
-  Node* node = visible_position.DeepEquivalent().AnchorNode();
+static PositionTemplate<Strategy> StartOfDocumentAlgorithm(
+    const PositionTemplate<Strategy>& position) {
+  const Node* const node = position.AnchorNode();
   if (!node || !node->GetDocument().documentElement())
-    return VisiblePositionTemplate<Strategy>();
+    return PositionTemplate<Strategy>();
 
-  return CreateVisiblePosition(PositionTemplate<Strategy>::FirstPositionInNode(
-      *node->GetDocument().documentElement()));
+  return PositionTemplate<Strategy>::FirstPositionInNode(
+      *node->GetDocument().documentElement());
 }
 
-VisiblePosition StartOfDocument(const VisiblePosition& c) {
+Position StartOfDocument(const Position& c) {
   return StartOfDocumentAlgorithm<EditingStrategy>(c);
 }
 
-VisiblePositionInFlatTree StartOfDocument(const VisiblePositionInFlatTree& c) {
+PositionInFlatTree StartOfDocument(const PositionInFlatTree& c) {
   return StartOfDocumentAlgorithm<EditingInFlatTreeStrategy>(c);
 }
 

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

@@ -230,9 +230,8 @@ bool InSameParagraph(const VisiblePosition&,
 EphemeralRange ExpandToParagraphBoundary(const EphemeralRange&);
 
 // document
-CORE_EXPORT VisiblePosition StartOfDocument(const VisiblePosition&);
-CORE_EXPORT VisiblePositionInFlatTree
-StartOfDocument(const VisiblePositionInFlatTree&);
+CORE_EXPORT Position StartOfDocument(const Position&);
+CORE_EXPORT PositionInFlatTree StartOfDocument(const PositionInFlatTree&);
 CORE_EXPORT VisiblePosition EndOfDocument(const VisiblePosition&);
 CORE_EXPORT VisiblePositionInFlatTree
 EndOfDocument(const VisiblePositionInFlatTree&);

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

@@ -780,17 +780,17 @@ TEST_F(VisibleUnitsTest, startOfDocument) {
   Node* two = GetDocument().getElementById("two")->firstChild();
 
   EXPECT_EQ(Position(one, 0),
-            StartOfDocument(CreateVisiblePositionInDOMTree(*one, 0))
+            CreateVisiblePosition(StartOfDocument(Position(*one, 0)))
                 .DeepEquivalent());
   EXPECT_EQ(PositionInFlatTree(two, 0),
-            StartOfDocument(CreateVisiblePositionInFlatTree(*one, 0))
+            CreateVisiblePosition(StartOfDocument(PositionInFlatTree(*one, 0)))
                 .DeepEquivalent());
 
   EXPECT_EQ(Position(one, 0),
-            StartOfDocument(CreateVisiblePositionInDOMTree(*two, 1))
+            CreateVisiblePosition(StartOfDocument(Position(*two, 1)))
                 .DeepEquivalent());
   EXPECT_EQ(PositionInFlatTree(two, 0),
-            StartOfDocument(CreateVisiblePositionInFlatTree(*two, 1))
+            CreateVisiblePosition(StartOfDocument(PositionInFlatTree(*two, 1)))
                 .DeepEquivalent());
 }