[LayoutNG] Reorder members of NGConstraintSpace to reduce size

This patch reorders members of NGConstraintSpace so that
value (non-class/struct) members are placed at the end.

Due to byte-align, it reduces the size from 96 bytes to
88 bytes on x64.

Bug: 635619
Change-Id: I7d9471343f3c16d91f7534fd98e2b95f1d18f8c5
Reviewed-on: https://chromium-review.googlesource.com/c/1314070Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604994}

third_party/blink/renderer/core/layout/ng/ng_constraint_space.cc

@@ -20,11 +20,11 @@ namespace {
 struct SameSizeAsNGConstraintSpace {
   NGLogicalSize logical_sizes[3];
   NGPhysicalSize physical_sizes[1];
-  LayoutUnit layout_units[3];
   NGMarginStrut margin_strut;
   NGBfcOffset bfc_offset;
   NGExclusionSpace exclusion_space;
   base::Optional<LayoutUnit> optional_layout_unit;
+  LayoutUnit layout_units[3];
   unsigned flags[1];
 };
 
@@ -41,22 +41,22 @@ NGConstraintSpace::NGConstraintSpace(WritingMode out_writing_mode,
       replaced_percentage_resolution_size_(
           builder.replaced_percentage_resolution_size_),
       initial_containing_block_size_(builder.initial_containing_block_size_),
+      margin_strut_(is_new_fc ? NGMarginStrut() : builder.margin_strut_),
+      bfc_offset_(is_new_fc ? NGBfcOffset() : builder.bfc_offset_),
+      floats_bfc_block_offset_(is_new_fc ? base::nullopt
+                                         : builder.floats_bfc_block_offset_),
       fragmentainer_block_size_(builder.fragmentainer_block_size_),
       fragmentainer_space_at_bfc_start_(
           builder.fragmentainer_space_at_bfc_start_),
+      clearance_offset_(is_new_fc ? LayoutUnit::Min()
+                                  : builder.clearance_offset_),
       block_direction_fragmentation_type_(builder.fragmentation_type_),
       table_cell_child_layout_phase_(builder.table_cell_child_layout_phase_),
       adjoining_floats_(builder.adjoining_floats_),
       writing_mode_(static_cast<unsigned>(out_writing_mode)),
       direction_(static_cast<unsigned>(builder.text_direction_)),
       flags_(builder.flags_),
-      baseline_requests_(builder.baseline_requests_.Serialize()),
-      margin_strut_(is_new_fc ? NGMarginStrut() : builder.margin_strut_),
-      bfc_offset_(is_new_fc ? NGBfcOffset() : builder.bfc_offset_),
-      floats_bfc_block_offset_(is_new_fc ? base::nullopt
-                                         : builder.floats_bfc_block_offset_),
-      clearance_offset_(is_new_fc ? LayoutUnit::Min()
-                                  : builder.clearance_offset_) {
+      baseline_requests_(builder.baseline_requests_.Serialize()) {
   bool is_in_parallel_flow =
       IsParallelWritingMode(builder.parent_writing_mode_, out_writing_mode);
 

third_party/blink/renderer/core/layout/ng/ng_constraint_space.h

@@ -308,9 +308,17 @@ class CORE_EXPORT NGConstraintSpace final {
   NGLogicalSize replaced_percentage_resolution_size_;
   NGPhysicalSize initial_containing_block_size_;
 
+  NGMarginStrut margin_strut_;
+  NGBfcOffset bfc_offset_;
+  base::Optional<LayoutUnit> floats_bfc_block_offset_;
+
+  NGExclusionSpace exclusion_space_;
+
   LayoutUnit fragmentainer_block_size_;
   LayoutUnit fragmentainer_space_at_bfc_start_;
 
+  LayoutUnit clearance_offset_;
+
   unsigned block_direction_fragmentation_type_ : 2;
   unsigned table_cell_child_layout_phase_ : 2;  // NGTableCellChildLayoutPhase
   unsigned adjoining_floats_ : 2;               // NGFloatTypes
@@ -318,13 +326,6 @@ class CORE_EXPORT NGConstraintSpace final {
   unsigned direction_ : 1;
   unsigned flags_ : kNumberOfConstraintSpaceFlags;  // ConstraintSpaceFlags
   unsigned baseline_requests_ : NGBaselineRequestList::kSerializedBits;
-
-  NGMarginStrut margin_strut_;
-  NGBfcOffset bfc_offset_;
-  base::Optional<LayoutUnit> floats_bfc_block_offset_;
-
-  NGExclusionSpace exclusion_space_;
-  LayoutUnit clearance_offset_;
 };
 
 inline std::ostream& operator<<(std::ostream& stream,