Bug 1295867: Wait for all IO operations to complete before ending test tasks. r=aswan

MozReview-Commit-ID: A6DIpXE5M1R

--HG--
extra : rebase_source : 386f3e602a169ad105dc4bf9abe74c4c6ffe10c2

toolkit/modules/subprocess/subprocess_worker_common.js

@@ -61,6 +61,19 @@ class BaseProcess {
     this.spawn(options);
   }
 
+  /**
+   * Waits for the process to exit and all of its pending IO operations to
+   * complete.
+   *
+   * @returns {Promise<void>}
+   */
+  awaitFinished() {
+    return Promise.all([
+      this.exitPromise,
+      ...this.pipes.map(pipe => pipe.closedPromise),
+    ]);
+  }
+
   /**
    * Creates a null-terminated array of pointers to null-terminated C-strings,
    * and returns it.
@@ -130,8 +143,11 @@ let requests = {
 
     process.wait();
 
-    return process.exitPromise.then(exitCode => {
+    process.awaitFinished().then(() => {
       io.cleanupProcess(process);
+    });
+
+    return process.exitPromise.then(exitCode => {
       return {data: {exitCode}};
     });
   },
@@ -163,7 +179,8 @@ let requests = {
   },
 
   waitForNoProcesses() {
-    return Promise.all(Array.from(io.processes.values(), proc => proc.exitPromise));
+    return Promise.all(Array.from(io.processes.values(),
+                                  proc => proc.awaitFinished()));
   },
 };