test: stdio pipe behavior tests

Add two regression tests for stdio over pipes.

test-stdio-pipe-access tests if accessing stdio pipe that is being read
by another process does not deadlocks Node.js. This was reported in
nodejs#10836 and was fixed in v8.3.0.
The deadlock would happen intermittently, so we run the test 5 times.

test-stdio-pipe-redirect tests if redirecting one child process stdin to
another process stdout does not crash Node as reported in
nodejs#17493. It was fixed in
nodejs#18019.

test/parallel/test-stdio-pipe-access.js

@@ -0,0 +1,36 @@
+'use strict';
+require('../common');
+
+// Test if Node handles acessing process.stdin if it is a redirected
+// pipe without deadlocking
+const { spawn, spawnSync } = require('child_process');
+
+const numTries = 5;
+const who = process.argv.length <= 2 ? 'runner' : process.argv[2];
+
+switch (who) {
+  case 'runner':
+    for (let num = 0; num < numTries; ++num) {
+      console.log('Try: ' + num);
+      spawnSync(process.argv0,
+                [process.argv[1], 'parent'],
+                { 'stdio': 'inherit' });
+    }
+    break;
+  case 'parent':
+    const middle = spawn(process.argv0,
+                         [process.argv[1], 'middle'],
+                         { 'stdio': 'pipe' });
+    middle.stdout.on('data', () => {});
+    break;
+  case 'middle':
+    spawn(process.argv0,
+          [process.argv[1], 'bottom'],
+          { 'stdio': [ process.stdin,
+                       process.stdout,
+                       process.stderr ] });
+    break;
+  case 'bottom':
+    process.stdin;
+    break;
+}

test/parallel/test-stdio-pipe-redirect.js

@@ -0,0 +1,38 @@
+'use strict';
+require('../common');
+
+// Test if Node handles redirecting one child process stdout to another
+// process stdin without crashing.
+const spawn = require('child_process').spawn;
+
+const writeSize = 100;
+const totalDots = 10000;
+
+const who = process.argv.length <= 2 ? 'parent' : process.argv[2];
+
+switch (who) {
+  case 'parent':
+    const consumer = spawn(process.argv0, [process.argv[1], 'consumer'], {
+      stdio: ['pipe', 'ignore', 'inherit'],
+    });
+    const producer = spawn(process.argv0, [process.argv[1], 'producer'], {
+      stdio: ['pipe', consumer.stdin, 'inherit'],
+    });
+    process.stdin.on('data', () => {});
+    producer.on('exit', process.exit);
+    break;
+  case 'producer':
+    const buffer = Buffer.alloc(writeSize, '.');
+    let written = 0;
+    const write = () => {
+      if (written < totalDots) {
+        written += writeSize;
+        process.stdout.write(buffer, write);
+      }
+    };
+    write();
+    break;
+  case 'consumer':
+    process.stdin.on('data', () => {});
+    break;
+}