[LayoutNG] Change PositionFloats signature

This patch changes PositionFloats to have
NGPositionedFloatVector* to return the positioned floats,
instead of it to return the vector.

NGPositionedFloatVector has inline buffer that returning
it involves a bit of memory copy overhead.

Pinpoint shows slight improvement. We could see them within
errors, but mostly positive, and running twice shows similar
trends.
https://pinpoint-dot-chromeperf.appspot.com/job/11f3134ce40000

Bug: 635619
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I29c23e370b398f54a9acc1745f37ea9ffcb1b2fc
Reviewed-on: https://chromium-review.googlesource.com/c/1282689Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600101}

third_party/blink/renderer/core/layout/ng/inline/ng_inline_layout_algorithm.cc

@@ -888,12 +888,12 @@ void NGInlineLayoutAlgorithm::PositionPendingFloats(
   NGBfcOffset origin_bfc_offset = {ConstraintSpace().BfcOffset().line_offset,
                                    bfc_block_offset + content_size};
 
-  const NGPositionedFloatVector positioned_floats =
-      PositionFloats(ConstraintSpace().AvailableSize(),
-                     ConstraintSpace().PercentageResolutionSize(),
-                     ConstraintSpace().ReplacedPercentageResolutionSize(),
-                     origin_bfc_offset, bfc_block_offset, unpositioned_floats_,
-                     ConstraintSpace(), exclusion_space);
+  NGPositionedFloatVector positioned_floats;
+  PositionFloats(ConstraintSpace().AvailableSize(),
+                 ConstraintSpace().PercentageResolutionSize(),
+                 ConstraintSpace().ReplacedPercentageResolutionSize(),
+                 origin_bfc_offset, bfc_block_offset, unpositioned_floats_,
+                 ConstraintSpace(), exclusion_space, &positioned_floats);
 
   positioned_floats_.AppendVector(positioned_floats);
   unpositioned_floats_.clear();

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

@@ -2081,10 +2081,11 @@ void NGBlockLayoutAlgorithm::PositionPendingFloats(
           ? container_builder_.BfcBlockOffset().value()
           : ConstraintSpace().FloatsBfcBlockOffset().value();
 
-  const auto positioned_floats = PositionFloats(
-      child_available_size_, child_percentage_size_,
-      replaced_child_percentage_size_, origin_bfc_offset, bfc_block_offset,
-      unpositioned_floats_, ConstraintSpace(), &exclusion_space_);
+  NGPositionedFloatVector positioned_floats;
+  PositionFloats(child_available_size_, child_percentage_size_,
+                 replaced_child_percentage_size_, origin_bfc_offset,
+                 bfc_block_offset, unpositioned_floats_, ConstraintSpace(),
+                 &exclusion_space_, &positioned_floats);
 
   AddPositionedFloats(positioned_floats);
 

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

@@ -306,26 +306,24 @@ NGPositionedFloat PositionFloat(
   return NGPositionedFloat(std::move(layout_result), float_bfc_offset);
 }
 
-const NGPositionedFloatVector PositionFloats(
-    const NGLogicalSize& float_available_size,
-    const NGLogicalSize& float_percentage_size,
-    const NGLogicalSize& float_replaced_percentage_size,
-    const NGBfcOffset& origin_bfc_offset,
-    LayoutUnit parent_bfc_block_offset,
-    NGUnpositionedFloatVector& unpositioned_floats,
-    const NGConstraintSpace& space,
-    NGExclusionSpace* exclusion_space) {
-  NGPositionedFloatVector positioned_floats;
-  positioned_floats.ReserveCapacity(unpositioned_floats.size());
+void PositionFloats(const NGLogicalSize& float_available_size,
+                    const NGLogicalSize& float_percentage_size,
+                    const NGLogicalSize& float_replaced_percentage_size,
+                    const NGBfcOffset& origin_bfc_offset,
+                    LayoutUnit parent_bfc_block_offset,
+                    NGUnpositionedFloatVector& unpositioned_floats,
+                    const NGConstraintSpace& space,
+                    NGExclusionSpace* exclusion_space,
+                    NGPositionedFloatVector* positioned_floats) {
+  positioned_floats->ReserveCapacity(positioned_floats->size() +
+                                     unpositioned_floats.size());
 
   for (NGUnpositionedFloat& unpositioned_float : unpositioned_floats) {
-    positioned_floats.push_back(PositionFloat(
+    positioned_floats->push_back(PositionFloat(
         float_available_size, float_percentage_size,
         float_replaced_percentage_size, origin_bfc_offset,
         parent_bfc_block_offset, &unpositioned_float, space, exclusion_space));
   }
-
-  return positioned_floats;
 }
 
 void AddUnpositionedFloat(NGUnpositionedFloatVector* unpositioned_floats,

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

@@ -53,15 +53,16 @@ PositionFloat(const NGLogicalSize& float_available_size,
 
 // Positions the list of {@code unpositioned_floats}. Adds them as exclusions to
 // {@code space}.
-CORE_EXPORT const NGPositionedFloatVector
-PositionFloats(const NGLogicalSize& float_available_size,
-               const NGLogicalSize& float_percentage_size,
-               const NGLogicalSize& float_replaced_percentage_size,
-               const NGBfcOffset& origin_bfc_offset,
-               LayoutUnit container_block_offset,
-               NGUnpositionedFloatVector& unpositioned_floats,
-               const NGConstraintSpace& space,
-               NGExclusionSpace* exclusion_space);
+CORE_EXPORT void PositionFloats(
+    const NGLogicalSize& float_available_size,
+    const NGLogicalSize& float_percentage_size,
+    const NGLogicalSize& float_replaced_percentage_size,
+    const NGBfcOffset& origin_bfc_offset,
+    LayoutUnit container_block_offset,
+    NGUnpositionedFloatVector& unpositioned_floats,
+    const NGConstraintSpace& space,
+    NGExclusionSpace* exclusion_space,
+    NGPositionedFloatVector* positioned_floats);
 
 // Add a pending float to the list. It will be committed (positioned) once we
 // have resolved the BFC block offset.