Stop calling LayoutObjectFromPosition in RenderedPosition

LayoutObjectFromPosition() is a hacky utility function to set
|RenderedPosition::layout_object_| when |inline_box_| is nullptr.

With previous refactoring, there is no usage of |layout_object_| when
|inline_box_| is nullptr, so we no longer need to set a non-null
|layout_object_| for null |inline_box_|.

Hence, this patch removes the call sites in RenderedPosition.

Note: the function cannot be removed because it is still indirectly
called by AX via LayoutObjectContainsPosition(). A follow-up patch
will move it to AX.

Bug: 822575
Change-Id: I720193c9926212153c56552115b5be9619ea20bc
Reviewed-on: https://chromium-review.googlesource.com/1025034Reviewed-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@{#552996}

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

@@ -92,11 +92,10 @@ RenderedPosition::RenderedPosition(const Position& position,
       ComputeInlineBoxPosition(PositionWithAffinity(position, affinity));
   inline_box_ = box_position.inline_box;
   offset_ = box_position.offset_in_box;
-  if (inline_box_)
+  if (inline_box_) {
     layout_object_ =
         LineLayoutAPIShim::LayoutObjectFrom(inline_box_->GetLineLayoutItem());
-  else
-    layout_object_ = LayoutObjectFromPosition(position);
+  }
 }
 
 RenderedPosition::RenderedPosition(const PositionInFlatTree& position,
@@ -108,11 +107,10 @@ RenderedPosition::RenderedPosition(const PositionInFlatTree& position,
       PositionInFlatTreeWithAffinity(position, affinity));
   inline_box_ = box_position.inline_box;
   offset_ = box_position.offset_in_box;
-  if (inline_box_)
+  if (inline_box_) {
     layout_object_ =
         LineLayoutAPIShim::LayoutObjectFrom(inline_box_->GetLineLayoutItem());
-  else
-    layout_object_ = LayoutObjectFromPosition(position);
+  }
 }
 
 const InlineBox* RenderedPosition::PrevLeafChild() const {