[FragmentItem] Fix NGInlineLayoutAlgorithmTest.BreakToken

The DCHECK was added to ensure |AddLine| is executed after
|SetCurrentLine|, which is not true for this unit test.

Bug: 982194
Change-Id: Idfdb0f5bd61f973937ffbc19c0da2e7d8d268047
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2262028
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781781}

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

@@ -42,11 +42,15 @@ void NGFragmentItemsBuilder::SetCurrentLine(
 #if DCHECK_IS_ON()
   current_line_fragment_ = &line;
 #endif
-  DCHECK(!current_line_);
   DCHECK(current_line);
+  DCHECK(!current_line_);  // Check |AddLine| runs after |SetCurrentLine|.
   current_line_ = current_line;
 }
 
+void NGFragmentItemsBuilder::ClearCurrentLineForTesting() {
+  current_line_ = nullptr;
+}
+
 void NGFragmentItemsBuilder::AddLine(const NGPhysicalLineBoxFragment& line,
                                      const LogicalOffset& offset) {
   DCHECK(!is_converted_to_physical_);

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_items_builder.h

@@ -62,6 +62,7 @@ class CORE_EXPORT NGFragmentItemsBuilder {
                       NGLogicalLineItems* current_line);
   void AddLine(const NGPhysicalLineBoxFragment& line,
                const LogicalOffset& offset);
+  void ClearCurrentLineForTesting();
 
   // Add a list marker to the current line.
   void AddListMarker(const NGPhysicalBoxFragment& marker_fragment,

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

@@ -67,12 +67,14 @@ TEST_F(NGInlineLayoutAlgorithmTest, BreakToken) {
   EXPECT_FALSE(line1.BreakToken()->IsFinished());
 
   // Perform 2nd layout with the break token from the 1st line.
+  items_builder.ClearCurrentLineForTesting();
   scoped_refptr<const NGLayoutResult> layout_result2 =
       inline_node.Layout(constraint_space, line1.BreakToken(), &context);
   const auto& line2 = layout_result2->PhysicalFragment();
   EXPECT_FALSE(line2.BreakToken()->IsFinished());
 
   // Perform 3rd layout with the break token from the 2nd line.
+  items_builder.ClearCurrentLineForTesting();
   scoped_refptr<const NGLayoutResult> layout_result3 =
       inline_node.Layout(constraint_space, line2.BreakToken(), &context);
   const auto& line3 = layout_result3->PhysicalFragment();