Remove const_casts in SelectionModifier and ScopedFocusNavigation

Member<> now supports const types. This CL removes an unnecessary
const_cast in ScopedFocusNavigation and makes a Member<> const in
SelectionModifier so we can do the same there.

Bug: None.
Change-Id: Ica178eed562e19f9042872d162b6b7f37ed51fe3
Reviewed-on: https://chromium-review.googlesource.com/826843Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung.kim@lge.com>
Cr-Commit-Position: refs/heads/master@{#524322}

third_party/WebKit/Source/core/editing/SelectionModifier.cpp

@@ -62,7 +62,8 @@ LayoutUnit NoXPosForVerticalArrowNavigation() {
   return LayoutUnit::Min();
 }
 
-bool SelectionModifier::ShouldAlwaysUseDirectionalSelection(LocalFrame* frame) {
+bool SelectionModifier::ShouldAlwaysUseDirectionalSelection(
+    const LocalFrame* frame) {
   return !frame ||
          frame->GetEditor().Behavior().ShouldConsiderSelectionAsDirectional();
 }
@@ -71,7 +72,7 @@ SelectionModifier::SelectionModifier(
     const LocalFrame& frame,
     const SelectionInDOMTree& selection,
     LayoutUnit x_pos_for_vertical_arrow_navigation)
-    : frame_(const_cast<LocalFrame*>(&frame)),
+    : frame_(&frame),
       current_selection_(selection),
       x_pos_for_vertical_arrow_navigation_(
           x_pos_for_vertical_arrow_navigation) {}

third_party/WebKit/Source/core/editing/SelectionModifier.h

@@ -70,9 +70,9 @@ class SelectionModifier {
  private:
   // TODO(editing-dev): We should make |GetFrame()| to return |LocalFrame&|
   // since it can not be |nullptr|.
-  LocalFrame* GetFrame() const { return frame_; }
+  const LocalFrame* GetFrame() const { return frame_; }
 
-  static bool ShouldAlwaysUseDirectionalSelection(LocalFrame*);
+  static bool ShouldAlwaysUseDirectionalSelection(const LocalFrame*);
   TextDirection DirectionOfEnclosingBlock() const;
   TextDirection DirectionOfSelection() const;
   VisiblePosition PositionForPlatform(bool is_get_start) const;
@@ -103,7 +103,7 @@ class SelectionModifier {
   static VisiblePosition RightWordPosition(const VisiblePosition&,
                                            bool skips_space_when_moving_right);
 
-  Member<LocalFrame> frame_;
+  Member<const LocalFrame> frame_;
   // TODO(editing-dev): We should get rid of |selection_| once we change
   // all member functions not to use |selection_|.
   // |selection_| is used as implicit parameter or a cache instead of pass it.

third_party/WebKit/Source/core/page/FocusController.cpp

@@ -246,7 +246,7 @@ ScopedFocusNavigation::ScopedFocusNavigation(
     ContainerNode& scoping_root_node,
     const Element* current,
     FocusController::OwnerMap& owner_map)
-    : current_(const_cast<Element*>(current)) {
+    : current_(current) {
   if (HTMLSlotElement* slot = ToHTMLSlotElementOrNull(scoping_root_node)) {
     if (slot->AssignedNodes().IsEmpty()) {
       navigation_ = new FocusNavigation(scoping_root_node, *slot, owner_map);