diff --git a/testing/web-platform/tests/webrtc-extensions/RTCRtpEncodingParameters-scaleResolutionDownTo.https.html b/testing/web-platform/tests/webrtc-extensions/RTCRtpEncodingParameters-scaleResolutionDownTo.https.html
new file mode 100644
index 0000000000000..9e3075af83025
--- /dev/null
+++ b/testing/web-platform/tests/webrtc-extensions/RTCRtpEncodingParameters-scaleResolutionDownTo.https.html
@@ -0,0 +1,1971 @@
+<
+!
+DOCTYPE
+html
+>
+<
+meta
+charset
+=
+"
+utf
+-
+8
+"
+>
+<
+title
+>
+RTCRtpEncodingParameters
+scaleResolutionDownTo
+attribute
+<
+/
+title
+>
+<
+meta
+name
+=
+"
+timeout
+"
+content
+=
+"
+long
+"
+>
+<
+script
+src
+=
+"
+/
+resources
+/
+testharness
+.
+js
+"
+>
+<
+/
+script
+>
+<
+script
+src
+=
+"
+/
+resources
+/
+testharnessreport
+.
+js
+"
+>
+<
+/
+script
+>
+<
+script
+>
+'
+use
+strict
+'
+;
+/
+/
+Creates
+a
+track
+that
+can
+be
+resized
+with
+track
+.
+resize
+(
+w
+h
+)
+.
+function
+createResizableTrack
+(
+width
+height
+)
+{
+/
+/
+Draw
+to
+a
+canvas
+with
+a
+30
+fps
+interval
+.
+const
+canvas
+=
+Object
+.
+assign
+(
+document
+.
+createElement
+(
+'
+canvas
+'
+)
+{
+width
+height
+}
+)
+;
+const
+ctx
+=
+canvas
+.
+getContext
+(
+'
+2d
+'
+)
+;
+ctx
+.
+fillStyle
+=
+'
+rgb
+(
+255
+0
+0
+)
+'
+;
+const
+interval
+=
+setInterval
+(
+(
+)
+=
+>
+{
+ctx
+.
+fillRect
+(
+0
+0
+canvas
+.
+width
+canvas
+.
+height
+)
+;
+}
+1000
+/
+30
+)
+;
+/
+/
+Capture
+the
+canvas
+and
+add
+/
+modify
+reize
+(
+)
+and
+stop
+(
+)
+methods
+.
+const
+stream
+=
+canvas
+.
+captureStream
+(
+)
+;
+const
+[
+track
+]
+=
+stream
+.
+getTracks
+(
+)
+;
+track
+.
+resize
+=
+(
+w
+h
+)
+=
+>
+{
+canvas
+.
+width
+=
+w
+;
+canvas
+.
+height
+=
+h
+;
+}
+;
+const
+nativeStop
+=
+track
+.
+stop
+;
+track
+.
+stop
+=
+(
+)
+=
+>
+{
+clearInterval
+(
+interval
+)
+;
+nativeStop
+.
+apply
+(
+track
+)
+;
+}
+;
+return
+track
+;
+}
+async
+function
+getLastEncodedResolution
+(
+pc
+)
+{
+const
+report
+=
+await
+pc
+.
+getStats
+(
+)
+;
+for
+(
+const
+stats
+of
+report
+.
+values
+(
+)
+)
+{
+if
+(
+stats
+.
+type
+!
+=
+'
+outbound
+-
+rtp
+'
+)
+{
+continue
+;
+}
+if
+(
+!
+stats
+.
+frameWidth
+|
+|
+!
+stats
+.
+frameWidth
+)
+{
+/
+/
+The
+resolution
+is
+missing
+until
+the
+first
+frame
+has
+been
+encoded
+.
+break
+;
+}
+return
+{
+width
+:
+stats
+.
+frameWidth
+height
+:
+stats
+.
+frameHeight
+}
+;
+}
+return
+{
+width
+:
+null
+height
+:
+null
+}
+;
+}
+async
+function
+waitForFrameWithResolution
+(
+t
+pc
+width
+height
+)
+{
+let
+resolution
+;
+do
+{
+resolution
+=
+await
+getLastEncodedResolution
+(
+pc
+)
+;
+await
+new
+Promise
+(
+r
+=
+>
+t
+.
+step_timeout
+(
+r
+50
+)
+)
+;
+}
+while
+(
+resolution
+.
+width
+!
+=
+width
+|
+|
+resolution
+.
+height
+!
+=
+height
+)
+;
+}
+promise_test
+(
+async
+t
+=
+>
+{
+const
+pc
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc
+.
+close
+(
+)
+)
+;
+const
+track
+=
+createResizableTrack
+(
+120
+60
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+track
+.
+stop
+(
+)
+)
+;
+assert_throws_dom
+(
+'
+OperationError
+'
+(
+)
+=
+>
+{
+pc
+.
+addTransceiver
+(
+track
+{
+sendEncodings
+:
+[
+{
+scaleResolutionDownTo
+:
+undefined
+}
+{
+scaleResolutionDownTo
+:
+{
+maxWidth
+:
+120
+maxHeight
+:
+60
+}
+}
+]
+}
+)
+;
+}
+)
+;
+}
+addTransceiver
+:
+Specifying
+scaling
+on
+some
+but
+not
+all
+encodings
+throws
+)
+;
+promise_test
+(
+async
+t
+=
+>
+{
+const
+pc
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc
+.
+close
+(
+)
+)
+;
+const
+track
+=
+createResizableTrack
+(
+120
+60
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+track
+.
+stop
+(
+)
+)
+;
+const
+{
+sender
+}
+=
+pc
+.
+addTransceiver
+(
+track
+{
+sendEncodings
+:
+[
+{
+}
+{
+}
+]
+}
+)
+;
+const
+params
+=
+sender
+.
+getParameters
+(
+)
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownTo
+=
+undefined
+;
+params
+.
+encodings
+[
+1
+]
+.
+scaleResolutionDownTo
+=
+{
+maxWidth
+:
+120
+maxHeight
+:
+60
+}
+;
+const
+p
+=
+sender
+.
+setParameters
+(
+params
+)
+;
+promise_rejects_dom
+(
+t
+'
+InvalidModificationError
+'
+p
+)
+;
+}
+setParameters
+:
+Specifying
+scaling
+on
+some
+but
+not
+all
+encodings
+throws
+)
+;
+promise_test
+(
+async
+t
+=
+>
+{
+const
+pc1
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc1
+.
+close
+(
+)
+)
+;
+const
+pc2
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc2
+.
+close
+(
+)
+)
+;
+pc1
+.
+onicecandidate
+=
+e
+=
+>
+pc2
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+pc2
+.
+onicecandidate
+=
+e
+=
+>
+pc1
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+const
+track
+=
+createResizableTrack
+(
+120
+60
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+track
+.
+stop
+(
+)
+)
+;
+pc1
+.
+addTransceiver
+(
+track
+{
+sendEncodings
+:
+[
+{
+scaleResolutionDownBy
+:
+2
+.
+0
+scaleResolutionDownTo
+:
+{
+maxWidth
+:
+120
+maxHeight
+:
+60
+}
+}
+]
+}
+)
+;
+await
+pc1
+.
+setLocalDescription
+(
+)
+;
+await
+pc2
+.
+setRemoteDescription
+(
+pc1
+.
+localDescription
+)
+;
+await
+pc2
+.
+setLocalDescription
+(
+)
+;
+await
+pc1
+.
+setRemoteDescription
+(
+pc2
+.
+localDescription
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+120
+60
+)
+;
+}
+addTransceiver
+:
+scaleResolutionDownBy
+is
+ignored
+when
++
+scaleResolutionDownTo
+is
+specified
+)
+;
+promise_test
+(
+async
+t
+=
+>
+{
+const
+pc1
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc1
+.
+close
+(
+)
+)
+;
+const
+pc2
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc2
+.
+close
+(
+)
+)
+;
+pc1
+.
+onicecandidate
+=
+e
+=
+>
+pc2
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+pc2
+.
+onicecandidate
+=
+e
+=
+>
+pc1
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+const
+track
+=
+createResizableTrack
+(
+120
+60
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+track
+.
+stop
+(
+)
+)
+;
+const
+{
+sender
+}
+=
+pc1
+.
+addTransceiver
+(
+track
+)
+;
+const
+params
+=
+sender
+.
+getParameters
+(
+)
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownBy
+=
+2
+.
+0
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownTo
+=
+{
+maxWidth
+:
+120
+maxHeight
+:
+60
+}
+;
+const
+p
+=
+sender
+.
+setParameters
+(
+params
+)
+;
+await
+pc1
+.
+setLocalDescription
+(
+)
+;
+await
+pc2
+.
+setRemoteDescription
+(
+pc1
+.
+localDescription
+)
+;
+await
+pc2
+.
+setLocalDescription
+(
+)
+;
+await
+pc1
+.
+setRemoteDescription
+(
+pc2
+.
+localDescription
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+120
+60
+)
+;
+}
+setParameters
+:
+scaleResolutionDownBy
+is
+ignored
+when
++
+scaleResolutionDownTo
+is
+specified
+)
+;
+promise_test
+(
+async
+t
+=
+>
+{
+const
+pc1
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc1
+.
+close
+(
+)
+)
+;
+const
+pc2
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc2
+.
+close
+(
+)
+)
+;
+pc1
+.
+onicecandidate
+=
+e
+=
+>
+pc2
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+pc2
+.
+onicecandidate
+=
+e
+=
+>
+pc1
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+const
+track
+=
+createResizableTrack
+(
+120
+60
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+track
+.
+stop
+(
+)
+)
+;
+const
+{
+sender
+}
+=
+pc1
+.
+addTransceiver
+(
+track
+{
+sendEncodings
+:
+[
+{
+scaleResolutionDownTo
+:
+{
+maxWidth
+:
+60
+maxHeight
+:
+30
+}
+}
+]
+}
+)
+;
+await
+pc1
+.
+setLocalDescription
+(
+)
+;
+await
+pc2
+.
+setRemoteDescription
+(
+pc1
+.
+localDescription
+)
+;
+await
+pc2
+.
+setLocalDescription
+(
+)
+;
+await
+pc1
+.
+setRemoteDescription
+(
+pc2
+.
+localDescription
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+60
+30
+)
+;
+}
+addTransceiver
+:
+scaleResolutionDownTo
+with
+half
+resolution
+)
+;
+promise_test
+(
+async
+t
+=
+>
+{
+const
+pc1
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc1
+.
+close
+(
+)
+)
+;
+const
+pc2
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc2
+.
+close
+(
+)
+)
+;
+pc1
+.
+onicecandidate
+=
+e
+=
+>
+pc2
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+pc2
+.
+onicecandidate
+=
+e
+=
+>
+pc1
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+const
+track
+=
+createResizableTrack
+(
+120
+60
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+track
+.
+stop
+(
+)
+)
+;
+const
+{
+sender
+}
+=
+pc1
+.
+addTransceiver
+(
+track
+)
+;
+await
+pc1
+.
+setLocalDescription
+(
+)
+;
+await
+pc2
+.
+setRemoteDescription
+(
+pc1
+.
+localDescription
+)
+;
+await
+pc2
+.
+setLocalDescription
+(
+)
+;
+await
+pc1
+.
+setRemoteDescription
+(
+pc2
+.
+localDescription
+)
+;
+/
+/
+Request
+full
+resolution
+.
+let
+params
+=
+sender
+.
+getParameters
+(
+)
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownTo
+=
+{
+maxWidth
+:
+120
+maxHeight
+:
+60
+}
+;
+await
+sender
+.
+setParameters
+(
+params
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+120
+60
+)
+;
+/
+/
+Request
+half
+resolution
+.
+params
+=
+sender
+.
+getParameters
+(
+)
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownTo
+=
+{
+maxWidth
+:
+60
+maxHeight
+:
+30
+}
+;
+await
+sender
+.
+setParameters
+(
+params
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+60
+30
+)
+;
+/
+/
+Request
+full
+resolution
+again
+.
+params
+=
+sender
+.
+getParameters
+(
+)
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownTo
+=
+{
+maxWidth
+:
+120
+maxHeight
+:
+60
+}
+;
+await
+sender
+.
+setParameters
+(
+params
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+120
+60
+)
+;
+}
+setParameters
+:
+Modify
+scaleResolutionDownTo
+while
+sending
+)
+;
+promise_test
+(
+async
+t
+=
+>
+{
+const
+pc1
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc1
+.
+close
+(
+)
+)
+;
+const
+pc2
+=
+new
+RTCPeerConnection
+(
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+pc2
+.
+close
+(
+)
+)
+;
+pc1
+.
+onicecandidate
+=
+e
+=
+>
+pc2
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+pc2
+.
+onicecandidate
+=
+e
+=
+>
+pc1
+.
+addIceCandidate
+(
+e
+.
+candidate
+)
+;
+const
+track
+=
+createResizableTrack
+(
+60
+30
+)
+;
+t
+.
+add_cleanup
+(
+(
+)
+=
+>
+track
+.
+stop
+(
+)
+)
+;
+const
+{
+sender
+}
+=
+pc1
+.
+addTransceiver
+(
+track
+)
+;
+await
+pc1
+.
+setLocalDescription
+(
+)
+;
+await
+pc2
+.
+setRemoteDescription
+(
+pc1
+.
+localDescription
+)
+;
+await
+pc2
+.
+setLocalDescription
+(
+)
+;
+await
+pc1
+.
+setRemoteDescription
+(
+pc2
+.
+localDescription
+)
+;
+/
+/
+scaleTo
+is
+portrait
+track
+is
+landscape
+but
+no
+scaling
+should
+happen
+due
+/
+/
+to
+orientation
+agnosticism
+.
+let
+params
+=
+sender
+.
+getParameters
+(
+)
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownTo
+=
+{
+maxWidth
+:
+30
+maxHeight
+:
+60
+}
+;
+await
+sender
+.
+setParameters
+(
+params
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+60
+30
+)
+;
+/
+/
+Change
+orientation
+of
+the
+track
+:
+still
+no
+downscale
+but
+encoder
+begins
+to
+/
+/
+produce
+the
+new
+orientation
+.
+track
+.
+resize
+(
+30
+60
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+30
+60
+)
+;
+/
+/
+scaleTo
+in
+landscape
+reducing
+to
+half
+size
+.
+Verify
+track
+which
+is
+/
+/
+portrait
+is
+scaled
+down
+by
+2
+.
+params
+=
+sender
+.
+getParameters
+(
+)
+;
+params
+.
+encodings
+[
+0
+]
+.
+scaleResolutionDownTo
+=
+{
+maxWidth
+:
+30
+maxHeight
+:
+15
+}
+;
+await
+sender
+.
+setParameters
+(
+params
+)
+;
+await
+waitForFrameWithResolution
+(
+t
+pc1
+15
+30
+)
+;
+}
+scaleResolutionDownTo
+is
+orientation
+agnostic
+)
+;
+<
+/
+script
+>