Bug 1514074 - Retarget results of offset* DOM APIs. r=smaug

Per w3c/csswg-drafts#159.

The test is imported from WebKit, who has already implemented this, with a few
fixes to avoid duplicate test names and non-undefined return values from
add_cleanup.

See the diff attached to the bug.

Differential Revision: https://phabricator.services.mozilla.com/D15938

UltraBlame original commit: e0a5cb126f2f084e5f7f3d5f0be0222a7fd67479

Author: marco-c

dom/html/nsGenericHTMLElement.cpp

@@ -1591,34 +1591,38 @@ return
 false
 ;
 }
+struct
+OffsetResult
+{
 Element
 *
-nsGenericHTMLElement
-:
-:
-GetOffsetRect
-(
-CSSIntRect
-&
-aRect
-)
-{
-aRect
+mParent
 =
+nullptr
+;
 CSSIntRect
+mRect
+;
+}
+;
+static
+OffsetResult
+GetUnretargetedOffsetsFor
 (
+const
+Element
+&
+aElement
 )
-;
+{
 nsIFrame
 *
 frame
 =
+aElement
+.
 GetPrimaryFrame
 (
-FlushType
-:
-:
-Layout
 )
 ;
 if
@@ -1628,7 +1632,8 @@ frame
 )
 {
 return
-nullptr
+{
+}
 ;
 }
 nsIFrame
@@ -1671,6 +1676,8 @@ Element
 *
 docElement
 =
+aElement
+.
 GetComposedDoc
 (
 )
@@ -2085,6 +2092,8 @@ here
 .
 offsetParent
 =
+aElement
+.
 GetComposedDoc
 (
 )
@@ -2266,29 +2275,207 @@ MoveTo
 origin
 )
 ;
-aRect
-=
+return
+{
+Element
+:
+:
+FromNodeOrNull
+(
+offsetParent
+)
 CSSIntRect
 :
 :
 FromAppUnitsRounded
 (
 rcFrame
 )
+}
+;
+}
+static
+bool
+ShouldBeRetargeted
+(
+const
+Element
+&
+aReferenceElement
+const
+Element
+&
+aElementToMaybeRetarget
+)
+{
+ShadowRoot
+*
+shadow
+=
+aElementToMaybeRetarget
+.
+GetContainingShadow
+(
+)
 ;
+if
+(
+!
+shadow
+)
+{
 return
-offsetParent
-?
-offsetParent
+false
+;
+}
+for
+(
+ShadowRoot
+*
+scope
+=
+aReferenceElement
+.
+GetContainingShadow
+(
+)
+;
+scope
+;
+scope
+=
+scope
 -
 >
-AsElement
+Host
+(
+)
+-
+>
+GetContainingShadow
 (
 )
+)
+{
+if
+(
+scope
+=
+=
+shadow
+)
+{
+return
+false
+;
+}
+}
+return
+true
+;
+}
+Element
+*
+nsGenericHTMLElement
+:
 :
+GetOffsetRect
+(
+CSSIntRect
+&
+aRect
+)
+{
+aRect
+=
+CSSIntRect
+(
+)
+;
+if
+(
+!
+GetPrimaryFrame
+(
+FlushType
+:
+:
+Layout
+)
+)
+{
+return
 nullptr
 ;
 }
+OffsetResult
+thisResult
+=
+GetUnretargetedOffsetsFor
+(
+*
+this
+)
+;
+aRect
+=
+thisResult
+.
+mRect
+;
+Element
+*
+parent
+=
+thisResult
+.
+mParent
+;
+while
+(
+parent
+&
+&
+ShouldBeRetargeted
+(
+*
+this
+*
+parent
+)
+)
+{
+OffsetResult
+result
+=
+GetUnretargetedOffsetsFor
+(
+*
+parent
+)
+;
+aRect
++
+=
+result
+.
+mRect
+.
+TopLeft
+(
+)
+;
+parent
+=
+result
+.
+mParent
+;
+}
+return
+parent
+;
+}
 bool
 nsGenericHTMLElement
 :