Add support of leader_point in NGLayoutOpportunityIterator.

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

Index: third_party/WebKit/Source/core/layout/ng/ng_units.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_units.h b/third_party/WebKit/Source/core/layout/ng/ng_units.h
index a8821b681b375806a0ef20feabbf198bb4e12e36..1ee8c1e538dda12907260db06f3530dd736cedcf 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_units.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_units.h
@@ -27,6 +27,10 @@ struct NGLogicalSize {
 
   NGPhysicalSize ConvertToPhysical(NGWritingMode mode) const;
   bool operator==(const NGLogicalSize& other) const;
+
+  bool IsEmpty() const {
+    return inline_size == LayoutUnit(0) || block_size == LayoutUnit(0);

[atotic, 2016/11/02 23:33:37]

Suggestion: 

you can also write this as:

return !inline_size || !block_size, LayoutUnit has operator bool()

[Gleb Lanbin, 2016/11/02 23:46:47]

thanks, but I prefer to keep it in this way because

1) implicit boolean cast is discouraged
http://clang.llvm.org/extra/clang-tidy/checks/readability-implicit-bool-cast....

2) I try to use positive booleans instead of negative one for the readability
sake. More details:
https://docs.google.com/document/d/1QzsV4wFMDeFbMx13gsV092i9RfGc5cbF8ERbPZ65Q...

+  }
 };
 
 // NGLogicalOffset is the position of a rect (typically a fragment) relative to
@@ -53,8 +57,21 @@ struct NGLogicalOffset {
   NGLogicalOffset operator+(const NGLogicalOffset& other) const;
 
   NGLogicalOffset& operator+=(const NGLogicalOffset& other);
+
+  bool operator>(const NGLogicalOffset& other) const;
+  bool operator>=(const NGLogicalOffset& other) const;
+
+  bool operator<(const NGLogicalOffset& other) const;
+  bool operator<=(const NGLogicalOffset& other) const;
+
+  String ToString() const;
 };
 
+CORE_EXPORT inline std::ostream& operator<<(std::ostream& os,
+                                            const NGLogicalOffset& value) {
+  return os << value.ToString();
+}
+
 // NGPhysicalOffset is the position of a rect (typically a fragment) relative to
 // its parent rect in the physical coordinate system.
 struct NGPhysicalOffset {