[LayoutNG] Remove useless optional.

This was a mistake when I was initially writing this code.

Bug: 635619
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Ic67f0dd0364c9a03724c626b61c56632c8fa6605
Reviewed-on: https://chromium-review.googlesource.com/600310Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491996}

third_party/WebKit/Source/core/layout/ng/ng_floats_utils.cc

@@ -152,10 +152,9 @@ LayoutUnit ComputeInlineSizeForUnpositionedFloat(
   // the cached value.
   if (unpositioned_float->layout_result) {
     DCHECK(!is_same_writing_mode);
-    return NGFragment(parent_space->WritingMode(),
-                      unpositioned_float->layout_result.value()
-                          ->PhysicalFragment()
-                          .Get())
+    return NGFragment(
+               parent_space->WritingMode(),
+               unpositioned_float->layout_result->PhysicalFragment().Get())
         .InlineSize();
   }
 
@@ -184,7 +183,7 @@ LayoutUnit ComputeInlineSizeForUnpositionedFloat(
       unpositioned_float->node.Layout(space.Get());
 
   const NGPhysicalFragment* fragment =
-      unpositioned_float->layout_result.value()->PhysicalFragment().Get();
+      unpositioned_float->layout_result->PhysicalFragment().Get();
 
   DCHECK(fragment->BreakToken()->IsFinished());
 
@@ -220,7 +219,7 @@ NGPositionedFloat PositionFloat(LayoutUnit origin_block_offset,
 #if DCHECK_IS_ON()
     DCHECK(!is_same_writing_mode);
 #endif
-    layout_result = unpositioned_float->layout_result.value();
+    layout_result = unpositioned_float->layout_result;
   } else {
 #if DCHECK_IS_ON()
     DCHECK(is_same_writing_mode);

third_party/WebKit/Source/core/layout/ng/ng_unpositioned_float.h

@@ -11,7 +11,6 @@
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_exclusion.h"
 #include "core/style/ComputedStyleConstants.h"
-#include "platform/wtf/Optional.h"
 #include "platform/wtf/RefPtr.h"
 
 namespace blink {
@@ -57,7 +56,7 @@ struct CORE_EXPORT NGUnpositionedFloat
 
   // The layout result for this unpositioned float. This is only present if
   // it's in a different writing mode than the BFC.
-  WTF::Optional<RefPtr<NGLayoutResult>> layout_result;
+  RefPtr<NGLayoutResult> layout_result;
 
   bool IsLeft() const;
   bool IsRight() const;