Inline the resolveCall helper function at its call-sites in `Messag…

…eHandler`

There's only three call-sites and one of them doesn't even need the complete functionality of `resolveCall`, hence it seems reasonable to just inline this code.
An additional benefit of this is that the `Function.prototype.apply()` instance can also be converted into "normal" function calls, which should be a tiny bit more efficient.

The patch also replaces a number of unnecessary arrow functions, in relevant parts of the `MessageHandler` code, with "normal" functions instead.
Finally, all `Promise.resolve().then(...)` calls are replaced with `new Promise(...)` instead since the latter is a tiny bit more efficient. This also explains the test failures on the Linux bot, with a prior version of the patch, since the `Promise.resolve().then(...)` format essentially creates two Promises thus causing additional delay.

src/shared/message_handler.js

@@ -30,13 +30,6 @@ const StreamKind = {
  START_COMPLETE: 8,
 };
 
-async function resolveCall(fn, args) {
- if (!fn) {
- return undefined;
- }
- return fn.apply(null, args);
-}
-
 function wrapReason(reason) {
  if (typeof reason !== 'object') {
  return reason;
@@ -100,8 +93,8 @@ function MessageHandler(sourceName, targetName, comObj) {
  if (data.callbackId) {
  let sourceName = this.sourceName;
  let targetName = data.sourceName;
- Promise.resolve().then(function() {
- return action(data.data);
+ new Promise(function(resolve) {
+ resolve(action(data.data));
  }).then((result) => {
  comObj.postMessage({
  sourceName,
@@ -318,15 +311,17 @@ MessageHandler.prototype = {
  streamSink.sinkCapability.resolve();
  streamSink.ready = streamSink.sinkCapability.promise;
  this.streamSinks[streamId] = streamSink;
- resolveCall(action, [data.data, streamSink]).then(() => {
+ new Promise(function(resolve) {
+ resolve(action(data.data, streamSink));
+ }).then(function() {
  comObj.postMessage({
  sourceName,
  targetName,
  stream: StreamKind.START_COMPLETE,
  streamId,
  success: true,
  });
- }, (reason) => {
+ }, function(reason) {
  comObj.postMessage({
  sourceName,
  targetName,
@@ -385,15 +380,18 @@ MessageHandler.prototype = {
  }
  // Reset desiredSize property of sink on every pull.
  this.streamSinks[data.streamId].desiredSize = data.desiredSize;
- resolveCall(this.streamSinks[data.streamId].onPull).then(() => {
+ const { onPull, } = this.streamSinks[data.streamId];
+ new Promise(function(resolve) {
+ resolve(onPull && onPull());
+ }).then(function() {
  comObj.postMessage({
  sourceName,
  targetName,
  stream: StreamKind.PULL_COMPLETE,
  streamId,
  success: true,
  });
- }, (reason) => {
+ }, function(reason) {
  comObj.postMessage({
  sourceName,
  targetName,
@@ -435,16 +433,18 @@ MessageHandler.prototype = {
  if (!this.streamSinks[data.streamId]) {
  break;
  }
- resolveCall(this.streamSinks[data.streamId].onCancel,
- [wrapReason(data.reason)]).then(() => {
+ const { onCancel, } = this.streamSinks[data.streamId];
+ new Promise(function(resolve) {
+ resolve(onCancel && onCancel(wrapReason(data.reason)));
+ }).then(function() {
  comObj.postMessage({
  sourceName,
  targetName,
  stream: StreamKind.CANCEL_COMPLETE,
  streamId,
  success: true,
  });
- }, (reason) => {
+ }, function(reason) {
  comObj.postMessage({
  sourceName,
  targetName,