From c8664319edde80645bccca8f38fcc6872c9154ae Mon Sep 17 00:00:00 2001
From: Andrey Lushnikov <lushnikov@chromium.org>
Date: Thu, 6 Jul 2017 18:20:01 -0700
Subject: [PATCH] Make browser._ensureChromeIsRunning idempotent

The _ensureChromeIsRunning should launch chrome only once
and return the same promise for all its clients.
---
 lib/Browser.js | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/Browser.js b/lib/Browser.js
index a24018ef..f5a1a30f 100644
--- a/lib/Browser.js
+++ b/lib/Browser.js
@@ -63,6 +63,7 @@ class Browser {
       this._chromeArguments.push(...options.args);
     this._terminated = false;
     this._chromeProcess = null;
+    this._launchPromise = null;
   }
 
   /**
@@ -96,8 +97,12 @@ class Browser {
   }
 
   async _ensureChromeIsRunning() {
-    if (this._chromeProcess)
-      return;
+    if (!this._launchPromise)
+      this._launchPromise = this._launchChrome();
+    return this._launchPromise;
+  }
+
+  async _launchChrome() {
     this._chromeProcess = childProcess.spawn(this._chromeExecutable, this._chromeArguments, {});
     let stderr = '';
     this._chromeProcess.stderr.on('data', data => stderr += data.toString('utf8'));