Resolve inline margins in over-constrained situations correctly.

third_party/WebKit/Source/core/layout/LayoutBox.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.cpp b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
index 6f2ceee06cd38b7eebf8828ca9cde565f9b1a570..22e237c79377f1eb45c604bb23545d2878ac52fe 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -2702,8 +2702,15 @@ void LayoutBox::ComputeLogicalWidth(
       computed_values.margins_.start_, computed_values.margins_.end_,
       Style()->MarginStart(), Style()->MarginEnd());
 
+  // CSS 2.1 10.3.3
+  // If 'width' is not 'auto' and 'border-left-width' + 'padding-left' + 'width'
+  //  + 'padding-right' + 'border-right-width' (plus any of 'margin-left' or
+  // 'margin-right' that are not 'auto') is larger than the width of the
+  // containing block, then any 'auto' values for 'margin-left' or
+  // 'margin-right' treated as zero. The following should only apply for parent
+  // width >=  children width
   if (!has_perpendicular_containing_block && container_logical_width &&
-      container_logical_width !=
+      container_logical_width >=

[facetothefate, 2017/04/26 18:09:43]

To keep the old behavior, should be > I guess

           (computed_values.extent_ + computed_values.margins_.start_ +
            computed_values.margins_.end_) &&
       !IsFloating() && !IsInline() && !cb->IsFlexibleBoxIncludingDeprecated() &&