Auto merge of #9668 - glennw:inline-accuracy, r=pcwalton

Ensure when calculating font metrics that the total line height matches requested line height.

This fixes rounding accuracy issues that could result in layout producing results off by a small number of Au.

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tests/wpt/metadata-css/css-transforms-1_dev/html/transform-input-017.htm.ini

@@ -1,5 +0,0 @@
-[transform-input-017.htm]
-  type: reftest
-  expected:
-    if os == "linux": PASS
-    FAIL

tests/wpt/metadata-css/css-transforms-1_dev/html/transform-input-018.htm.ini

@@ -1,3 +1,5 @@
 [transform-input-018.htm]
   type: reftest
-  expected: FAIL
+  expected:
+    if os == "mac": PASS
+    FAIL

tests/wpt/metadata-css/css21_dev/html4/position-relative-035.htm.ini

@@ -1,3 +1,5 @@
 [position-relative-035.htm]
   type: reftest
-  expected: FAIL
+  expected:
+    if os == "linux": PASS
+    FAIL