Auto merge of #16285 - stshine:inline-block-margin, r=emilio

layout: Use the margin box of an inline block when computing the inline size

<!-- Please describe your changes on the following line: -->

When computing the inline size of an inline block in inline formating
context, use the margin box of the underling block.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12413 (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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tests/wpt/mozilla/meta/MANIFEST.json

@@ -2759,6 +2759,18 @@
      {}
     ]
    ],
+   "css/inline_block_percentage_margin.html": [
+    [
+     "/_mozilla/css/inline_block_percentage_margin.html",
+     [
+      [
+       "/_mozilla/css/inline_block_percentage_margin_ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
    "css/inline_block_stacking_context_a.html": [
     [
      "/_mozilla/css/inline_block_stacking_context_a.html",
@@ -7887,6 +7899,11 @@
      {}
     ]
    ],
+   "css/inline_block_percentage_margin_ref.html": [
+    [
+     {}
+    ]
+   ],
    "css/inline_block_stacking_context_ref.html": [
     [
      {}
@@ -21814,6 +21831,14 @@
    "bad4704435c74a3204925206802eb004f380500e",
    "support"
   ],
+  "css/inline_block_percentage_margin.html": [
+   "0b750acad3bcc6b5fabf9e625b6adf22e1e97640",
+   "reftest"
+  ],
+  "css/inline_block_percentage_margin_ref.html": [
+   "3726b3b2149b9e6584277fd33b77940d5f9d6800",
+   "support"
+  ],
   "css/inline_block_stacking_context_a.html": [
    "6c872ab3c551e4fe6c293468aa310ae61487b583",
    "reftest"