Auto merge of #8932 - rilut:add-elementfrompoint, r=nox

Implement Document#elementFromPoint

Related to #8666. I haven't implemented elementsFromPoint, because from my past discussion with jdm, [it's not good yet](dbfa25214b (commitcomment-14668959)) to implement elementsFromPoint because it may cause GC hazards.

By the way, I also have to include the test for this, right? I've found this [1]. So, is all I have to do is just to put this into `tests/wpt/web-platform-tests/cssom-view/elementFromPoint.html`?

[1] http://test.csswg.org/suites/cssom-view-1_dev/nightly-unstable/html/elementFromPosition.htm

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tests/wpt/metadata/html/semantics/embedded-content/the-area-element/area-coords.html.ini

@@ -21,15 +21,6 @@
   [CARRIGAGE RETURN: "2\\r2\\r10\\r10" (rect)]
     expected: FAIL
 
-  [LINE TABULATION: "2\\v2\\v10\\v10" (rect)]
-    expected: FAIL
-
-  [LINE NEXT: "2…2…10…10" (rect)]
-    expected: FAIL
-
-  [EN QUAD: "2 2 10 10" (rect)]
-    expected: FAIL
-
   [abc between numbers: "2a2b20c20,2,10,10" (rect)]
     expected: FAIL
 
@@ -48,15 +39,6 @@
   [leading SEMICOLON: ";2,2,10,10" (rect)]
     expected: FAIL
 
-  [trailing COMMA: "2,2,10," (rect)]
-    expected: FAIL
-
-  [trailing SPACE: "2,2,10 " (rect)]
-    expected: FAIL
-
-  [trailing SEMICOLON: "2,2,10;" (rect)]
-    expected: FAIL
-
   [PERCENT: "2%,2%,10%,10%" (rect)]
     expected: FAIL
 
@@ -78,18 +60,6 @@
   [non-ascii garbage: "“2,2,10,10\\"" (rect)]
     expected: FAIL
 
-  [URL garbage with number: "2,2,10ls/spain/holidays/regions/10/Canary+Islands/Canary+Islands.html" (rect)]
-    expected: FAIL
-
-  [consecutive COMMAs: "2,,10,10" (rect)]
-    expected: FAIL
-
-  [consecutive SPACEs: "2  10,10" (rect)]
-    expected: FAIL
-
-  [consecutive SEMICOLONs: "2;;10,10" (rect)]
-    expected: FAIL
-
   [several consecutive separators: ",,2;,;2,;,10 \\t\\r\\n10;;" (rect)]
     expected: FAIL
 

tests/wpt/metadata/html/semantics/embedded-content/the-area-element/area-processing.html.ini

@@ -1,17 +1,8 @@
 [area-processing.html]
   type: testharness
-  [too few numbers: "2,2,10" (rect)]
-    expected: FAIL
-
   [negative: "-10,-10,10,10" (rect)]
     expected: FAIL
 
-  [empty string: "" (rect)]
-    expected: FAIL
-
-  [omitted coords: null (rect)]
-    expected: FAIL
-
   [first > third: "10,2,2,10" (rect)]
     expected: FAIL
 
@@ -24,18 +15,6 @@
   [negative: "-10,-10,-10,-10" (default)]
     expected: FAIL
 
-  [too few numbers: "20,40" (circle)]
-    expected: FAIL
-
-  [negative radius: "20,40,-10" (circle)]
-    expected: FAIL
-
-  [zero radius: "20,40,0" (circle)]
-    expected: FAIL
-
-  [too few numbers: "100,100,120,100,100" (poly)]
-    expected: FAIL
-
   [one too many numbers: "100,100,120,100,100,120,300" (poly)]
     expected: FAIL
 

tests/wpt/metadata/html/semantics/embedded-content/the-area-element/area-shape.html.ini

@@ -3,12 +3,6 @@
   [missing value default: "2,2,10,10" (null)]
     expected: FAIL
 
-  [missing value default: "20,40,10" (null)]
-    expected: FAIL
-
-  [missing value default: null (null)]
-    expected: FAIL
-
   [invalid value default: "2,2,10,10" (foobar invalid)]
     expected: FAIL
 
@@ -33,12 +27,6 @@
   [simple: "20,40,10" (CIRC)]
     expected: FAIL
 
-  [LATIN CAPITAL LETTER I WITH DOT ABOVE: "20,40,10" (CİRCLE)]
-    expected: FAIL
-
-  [LATIN SMALL LETTER DOTLESS I: "20,40,10" (cırcle)]
-    expected: FAIL
-
   [simple: "100,100,120,100,100,120" (poly)]
     expected: FAIL