Resolve inline margins in over-constrained situations correctly.

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

Index: third_party/WebKit/Source/core/layout/LayoutBoxTest.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBoxTest.cpp b/third_party/WebKit/Source/core/layout/LayoutBoxTest.cpp
index 0b6c93be89dd7563d402c3c1698fb33ec0dceb5c..a8d3711168821de1d1ab51ded078b1e21a146540 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBoxTest.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBoxTest.cpp
@@ -263,4 +263,32 @@ TEST_F(LayoutBoxTest, LocalVisualRectWithMaskAndOverflowClip) {
   EXPECT_EQ(LayoutRect(0, 0, 100, 100), target->LocalVisualRect());
 }
 
+TEST_F(LayoutBoxTest, OverConstrainedAutoMarginLtr) {

[mstensho (USE GERRIT), 2017/05/12 11:07:20]

Let's use LayoutTests only for this.

[facetothefate, 2017/05/12 15:00:23]

Acknowledged.

+  SetBodyInnerHTML(
+      "<div style='"
+      "  width: 400px; border: 3px solid black;"
+      "'>"
+      "  <div id='target' style='"
+      "    margin-left: 10px; width: 500px; border: 3px solid gray; "
+      "margin-right: auto;"
+      "  '></div>"
+      "</div>");
+  LayoutBox* target = ToLayoutBox(GetLayoutObjectByElementId("target"));
+  EXPECT_EQ(LayoutUnit(-116), target->MarginEnd());
+}
+
+TEST_F(LayoutBoxTest, OverConstrainedAutoMarginRtl) {
+  SetBodyInnerHTML(
+      "<div style='"
+      "  width: 400px; border: 3px solid black; direction: rtl;"
+      "'>"
+      "  <div id='target' style='"
+      "    margin-right: 10px; width: 500px; border: 3px solid gray;"
+      "margin-left: auto;"
+      "  '></div>"
+      "</div>");
+  LayoutBox* target = ToLayoutBox(GetLayoutObjectByElementId("target"));
+  EXPECT_EQ(LayoutUnit(-116), target->MarginEnd());
+}
+
 }  // namespace blink