[css-contain] Make size containment elements monolithic

Spec text (https://drafts.csswg.org/css-contain/#containment-size):
  "2. Elements with size containment are monolithic."

This patch updates LayoutBox::GetPaginationBreakability()
to check if the element has size containment.

BUG=855263
TEST=external/wpt/css/css-contain/contain-size-breaks-001.html
TEST=external/wpt/css/css-contain/contain-size-monolithic-001.html

Change-Id: I372888eec2e3ab7ca51ad9c9b397ea6b8c89b629
Reviewed-on: https://chromium-review.googlesource.com/1256566Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Manuel Rego <rego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#595782}

third_party/WebKit/LayoutTests/TestExpectations

@@ -306,9 +306,7 @@ crbug.com/847274 external/wpt/css/css-contain/contain-paint-006.html [ Failure ]
 crbug.com/880802 external/wpt/css/css-contain/contain-paint-021.html [ Failure ]
 crbug.com/882367 external/wpt/css/css-contain/contain-paint-clip-015.html [ Failure ]
 crbug.com/882367 external/wpt/css/css-contain/contain-paint-clip-016.html [ Failure ]
-crbug.com/855263 external/wpt/css/css-contain/contain-size-breaks-001.html [ Failure ]
 crbug.com/855261 external/wpt/css/css-contain/contain-size-grid-002.html [ Failure ]
-crbug.com/855263 external/wpt/css/css-contain/contain-size-monolithic-001.html [ Failure ]
 crbug.com/863454 external/wpt/css/css-contain/contain-size-multicol-001.html [ Failure ]
 crbug.com/869296 external/wpt/css/css-contain/contain-style-counters-004.html [ Failure ]
 crbug.com/882383 external/wpt/css/css-contain/counter-scoping-001.html [ Failure ]

third_party/blink/renderer/core/layout/layout_box.cc

@@ -5405,7 +5405,8 @@ LayoutBox::PaginationBreakability LayoutBox::GetPaginationBreakability() const {
   if (IsAtomicInlineLevel() || HasUnsplittableScrollingOverflow() ||
       (Parent() && IsWritingModeRoot()) ||
       (IsOutOfFlowPositioned() &&
-       StyleRef().GetPosition() == EPosition::kFixed))
+       StyleRef().GetPosition() == EPosition::kFixed) ||
+      ShouldApplySizeContainment())
     return kForbidBreaks;
 
   EBreakInside break_value = BreakInside();