From cd82b81bc797b3664ec1aa63afcd9b1e536563fb Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sun, 1 Sep 2019 12:25:31 +0200
Subject: [PATCH] Inline the `resolveCall` helper function at its call-sites in
 `MessageHandler`

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 | 36 +++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/src/shared/message_handler.js b/src/shared/message_handler.js
index c148598af6c08..2a7a64d0b712e 100644
--- a/src/shared/message_handler.js
+++ b/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;
@@ -100,9 +93,9 @@ function MessageHandler(sourceName, targetName, comObj) {
       if (data.callbackId) {
         let sourceName = this.sourceName;
         let targetName = data.sourceName;
-        Promise.resolve().then(function() {
-          return action(data.data);
-        }).then((result) => {
+        new Promise(function(resolve) {
+          resolve(action(data.data));
+        }).then(function(result) {
           comObj.postMessage({
             sourceName,
             targetName,
@@ -110,7 +103,7 @@ function MessageHandler(sourceName, targetName, comObj) {
             callbackId: data.callbackId,
             data: result,
           });
-        }, (reason) => {
+        }, function(reason) {
           comObj.postMessage({
             sourceName,
             targetName,
@@ -318,7 +311,9 @@ 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,
@@ -326,7 +321,7 @@ MessageHandler.prototype = {
         streamId,
         success: true,
       });
-    }, (reason) => {
+    }, function(reason) {
       comObj.postMessage({
         sourceName,
         targetName,
@@ -385,7 +380,10 @@ 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,
@@ -393,7 +391,7 @@ MessageHandler.prototype = {
             streamId,
             success: true,
           });
-        }, (reason) => {
+        }, function(reason) {
           comObj.postMessage({
             sourceName,
             targetName,
@@ -435,8 +433,10 @@ 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,
@@ -444,7 +444,7 @@ MessageHandler.prototype = {
             streamId,
             success: true,
           });
-        }, (reason) => {
+        }, function(reason) {
           comObj.postMessage({
             sourceName,
             targetName,