Implement and ship RTCRtpEncodingParameters.scaleResolutionDownBy

Intent thread: https://groups.google.com/a/chromium.org/d/msg/blink-dev/SV8evGSU_dw/DIrx9XzvDQAJ

Bug: 857048
Change-Id: I32babd443aef05e6f1d062514b27ba5772ab400f
Reviewed-on: https://chromium-review.googlesource.com/c/1445934Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Florent Castelli <orphis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#627927}

third_party/blink/renderer/modules/peerconnection/rtc_rtp_encoding_parameters.idl

@@ -20,5 +20,5 @@ dictionary RTCRtpEncodingParameters : RTCRtpCodingParameters {
     //TODO(orphis): Missing ptime. https://crbug.com/857046
     unsigned long   maxBitrate;
     //TODO(orphis): Missing maxFramerate. https://crbug.com/857047
-    //TODO(orphis): Missing scaleResolutionDownBy. https://crbug.com/857048
+    double          scaleResolutionDownBy;
 };

third_party/blink/renderer/modules/peerconnection/rtc_rtp_sender.cc

@@ -250,8 +250,13 @@ webrtc::RtpEncodingParameters ToRtpEncodingParameters(
   webrtc_encoding.bitrate_priority = PriorityToDouble(encoding->priority());
   webrtc_encoding.network_priority =
       PriorityToDouble(encoding->networkPriority());
-  if (encoding->hasMaxBitrate())
+  if (encoding->hasMaxBitrate()) {
     webrtc_encoding.max_bitrate_bps = clampTo<int>(encoding->maxBitrate());
+  }
+  if (encoding->hasScaleResolutionDownBy()) {
+    webrtc_encoding.scale_resolution_down_by =
+        encoding->scaleResolutionDownBy();
+  }
   return webrtc_encoding;
 }
 
@@ -358,8 +363,13 @@ RTCRtpSendParameters* RTCRtpSender::getParameters() {
     // codecPayloadType, dtx, ptime, maxFramerate, scaleResolutionDownBy, rid
     RTCRtpEncodingParameters* encoding = RTCRtpEncodingParameters::Create();
     encoding->setActive(webrtc_encoding.active);
-    if (webrtc_encoding.max_bitrate_bps)
+    if (webrtc_encoding.max_bitrate_bps) {
       encoding->setMaxBitrate(webrtc_encoding.max_bitrate_bps.value());
+    }
+    if (webrtc_encoding.scale_resolution_down_by) {
+      encoding->setScaleResolutionDownBy(
+          webrtc_encoding.scale_resolution_down_by.value());
+    }
     encoding->setPriority(
         PriorityFromDouble(webrtc_encoding.bitrate_priority).c_str());
     encoding->setNetworkPriority(

third_party/blink/web_tests/external/wpt/webrtc/RTCRtpParameters-encodings-expected.txt

@@ -5,8 +5,8 @@ FAIL sender.getParameters() should return sendEncodings set by addTransceiver()
 PASS sender.setParameters() with mismatch number of encodings should reject with InvalidModificationError
 PASS sender.setParameters() with encodings unset should reject with TypeError
 FAIL setParameters() with modified encoding.rid field should reject with InvalidModificationError assert_equals: expected (string) "foo" but got (undefined) undefined
-FAIL setParameters() with encoding.scaleResolutionDownBy field set to less than 1.0 should reject with RangeError assert_unreached: Should have rejected: undefined Reached unreachable code
-FAIL setParameters() with encoding.scaleResolutionDownBy field set to greater than 1.0 should succeed assert_approx_equals: expected a number but got a "undefined"
+PASS setParameters() with encoding.scaleResolutionDownBy field set to less than 1.0 should reject with RangeError
+PASS setParameters() with encoding.scaleResolutionDownBy field set to greater than 1.0 should succeed
 FAIL setParameters() with modified encoding.dtx should succeed with RTCRtpTransceiverInit assert_equals: expected (string) "enabled" but got (undefined) undefined
 FAIL setParameters() with modified encoding.dtx should succeed without RTCRtpTransceiverInit assert_equals: expected (string) "enabled" but got (undefined) undefined
 FAIL setParameters() with unset encoding.dtx should succeed with RTCRtpTransceiverInit assert_equals: expected (string) "enabled" but got (undefined) undefined

third_party/blink/web_tests/external/wpt/webrtc/RTCRtpParameters-encodings.html

@@ -253,7 +253,7 @@
     const encoding = getFirstEncoding(param);
 
     encoding.scaleResolutionDownBy = 0.5;
-    return promise_rejects(t, 'RangeError',
+    return promise_rejects(t, new RangeError(),
       sender.setParameters(param));
   }, `setParameters() with encoding.scaleResolutionDownBy field set to less than 1.0 should reject with RangeError`);