[layoutng] margin: auto support

third_party/WebKit/Source/core/layout/ng/ng_length_utils.h

Index: third_party/WebKit/Source/core/layout/ng/ng_length_utils.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_length_utils.h b/third_party/WebKit/Source/core/layout/ng/ng_length_utils.h
index f5285dc6f2af80089773d9116f80a1167eb9c148..2a08e928c5546666b3d008978f9709fadf79d3d6 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_length_utils.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_length_utils.h
@@ -15,6 +15,7 @@ class LayoutUnit;
 class Length;
 class NGConstraintSpace;
 struct NGBoxStrut;
+class NGFragment;
 
 enum class LengthResolveType {
   MinSize,
@@ -63,6 +64,15 @@ CORE_EXPORT NGBoxStrut computeBorders(const ComputedStyle&);
 CORE_EXPORT NGBoxStrut computePadding(const NGConstraintSpace&,
                                       const ComputedStyle&);
 
+// Resolves margin: auto in the inline direction after a box has been laid out.
+// This uses the container size from the constraint space and the box size from
+// the fragment to compute the margins that are auto, if any, and adjusts
+// the given NGBoxStrut accordingly.
+CORE_EXPORT void ApplyAutoMargins(const NGConstraintSpace&,
+                                  const ComputedStyle&,
+                                  const NGFragment&,
+                                  NGBoxStrut& margins);
+
 }  // namespace blink
 
 #endif  // NGLengthUtils_h