Remove redundant 'derived constraint space' setters from NGConstraintSpace

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/ng/ng_block_layout_algorithm.h"
 
 #include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_constraint_space_builder.h"
 #include "core/layout/ng/ng_fragment_base.h"
@@ skipping 168 matching lines @@
       if (adjusted_block_size != NGSizeIndefinite)
         adjusted_block_size -= border_and_padding_.BlockSum();
 
       space_builder_ =
           new NGConstraintSpaceBuilder(constraint_space_->WritingMode());
       space_builder_->SetAvailableSize(
           NGLogicalSize(adjusted_inline_size, adjusted_block_size));
       space_builder_->SetPercentageResolutionSize(
           NGLogicalSize(adjusted_inline_size, adjusted_block_size));
 
-      constraint_space_->SetSize(

[cbiesinger, 2016/11/18 23:44:23]

Why is the new code still correct? This was necessary for correctness...?

[Gleb Lanbin, 2016/11/19 04:20:47]

ConstraintSpace::Size() was only used in
NGLayoutOpportunity::CreateLayoutOpportunityFromConstraintSpace. It always
equals to AvailableSize. So this patch removes redundant Size() method because
we already store the size information in physical constraint space. 

[cbiesinger, 2016/11/19 04:28:47]

So I'm confused. I thought this specific SetSize call was necessary because we
will use constraint_space_ to create the opportunity iterator, and nothing else
makes sure that the size is correct (especially, I don't see a call to set
AvailableSize on constraint_space_). What am I missing...?

-          NGLogicalSize(adjusted_inline_size, adjusted_block_size));
-
       content_size_ = border_and_padding_.block_start;
 
       builder_ = new NGFragmentBuilder(NGPhysicalFragmentBase::FragmentBox);
       builder_->SetDirection(constraint_space_->Direction());
       builder_->SetWritingMode(constraint_space_->WritingMode());
       builder_->SetInlineSize(inline_size).SetBlockSize(block_size);
       current_child_ = first_child_;
       if (current_child_)
         space_for_current_child_ = CreateConstraintSpaceForCurrentChild();
 
@@ skipping 196 matching lines @@
   visitor->trace(first_child_);
   visitor->trace(constraint_space_);
   visitor->trace(break_token_);
   visitor->trace(builder_);
   visitor->trace(space_builder_);
   visitor->trace(space_for_current_child_);
   visitor->trace(current_child_);
 }
 
 }  // namespace blink