Bug 1774315 - Don't clamp target scroll position to layer scale. r=mstange

This prevents scrollLeft = <integer> to return scrollLeft = <integer>,
which is right now papered by bug 1674687.

Differential Revision: https://phabricator.services.mozilla.com/D176306

UltraBlame original commit: 7ece24d43282c6c81fa92a42c2dde242ee848ed6

Author: marco-c

dom/events/test/window_bug1369072.html

@@ -333,13 +333,6 @@
 >
 <
 script
-type
-=
-"
-application
-/
-javascript
-"
 >
 SimpleTest
 .
@@ -376,6 +369,26 @@
 ;
 }
 function
+info
+(
+)
+{
+window
+.
+opener
+.
+info
+.
+apply
+(
+window
+.
+opener
+arguments
+)
+;
+}
+function
 is
 (
 )
@@ -733,6 +746,52 @@
 (
 )
 ;
+function
+promiseScrollOnWindow
+(
+win
+)
+{
+is
+(
+win
+.
+document
+.
+documentElement
+.
+scrollTop
+0
+"
+Reset
+didn
+'
+t
+work
+?
+"
+)
+;
+is
+(
+win
+.
+document
+.
+documentElement
+.
+scrollLeft
+0
+"
+Reset
+didn
+'
+t
+work
+?
+"
+)
+;
 return
 new
 Promise
@@ -741,16 +800,109 @@
 =
 >
 {
+win
+.
+addEventListener
+(
+"
+scroll
+"
+function
+listener
+(
+)
+{
 /
 /
-Wait
+FIXME
+(
+bug
+1674687
+)
+:
+The
+first
 scroll
-event
-function
-onScroll
+might
+be
+fractional
+(
+and
+/
+/
+scrollTop
+/
+Left
+will
+round
+down
+to
+zero
+until
+bug
+1674687
+is
+/
+/
+fixed
+)
+.
+So
+make
+sure
+we
+'
+ve
+scrolled
+at
+least
+a
+pixel
+before
+/
+/
+resolving
+.
+This
+can
+be
+removed
+once
+bug
+1674687
+is
+fixed
+.
+if
 (
+win
+.
+document
+.
+documentElement
+.
+scrollLeft
+|
+|
+win
+.
+document
+.
+documentElement
+.
+scrollTop
 )
 {
+win
+.
+removeEventListener
+(
+"
+scroll
+"
+listener
+)
+;
 SimpleTest
 .
 executeSoon
@@ -759,36 +911,32 @@
 )
 ;
 }
-window
-.
-addEventListener
-(
-"
-scroll
-"
-onScroll
-{
-once
-:
-true
 }
 )
 ;
+}
+)
+;
+}
+let
+promise
+=
+Promise
+.
+race
+(
+[
+promiseScrollOnWindow
+(
+window
+)
+promiseScrollOnWindow
+(
 iframe
 .
 contentWindow
-.
-addEventListener
-(
-"
-scroll
-"
-onScroll
-{
-once
-:
-true
-}
+)
+]
 )
 ;
 if
@@ -814,12 +962,13 @@
 )
 ;
 }
-}
-)
+return
+promise
 ;
 }
-/
-/
+info
+(
+"
 When
 iframe
 element
@@ -841,6 +990,9 @@
 scrolled
 instead
 .
+"
+)
+;
 document
 .
 body
@@ -932,8 +1084,9 @@
 (
 )
 ;
-/
-/
+info
+(
+"
 When
 iframe
 element
@@ -953,6 +1106,9 @@
 be
 scrolled
 .
+"
+)
+;
 document
 .
 body
@@ -1126,8 +1282,9 @@
 (
 )
 ;
-/
-/
+info
+(
+"
 If
 iframe
 document
@@ -1143,6 +1300,9 @@
 scrolled
 instead
 .
+"
+)
+;
 div
 .
 style
@@ -1421,8 +1581,9 @@
 (
 )
 ;
-/
-/
+info
+(
+"
 Hidden
 iframe
 shouldn
@@ -1437,6 +1598,9 @@
 not
 scrollable
 .
+"
+)
+;
 document
 .
 body