Introduce a dynamic process pool for the local test driver

tools/testrunner/local/pool_unittest.py

+#!/usr/bin/env python
+# Copyright 2014 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import unittest
+
+from pool import Pool
+
+def Run(x):
+  if x == 10:
+    raise Exception("Expected exception triggered by test.")
+  return x
+
+class PoolTest(unittest.TestCase):
+  def testNormal(self):
+    results = set()
+    pool = Pool(3)
+    for result in pool.imap_unordered(Run, [[x] for x in range(0, 10)]):
+      results.add(result)
+    self.assertEquals(set(range(0, 10)), results)
+
+  def testException(self):
+    results = set()
+    pool = Pool(3)
+    for result in pool.imap_unordered(Run, [[x] for x in range(0, 12)]):
+      # Item 10 will not appear in results due to an internal exception.
+      results.add(result)
+    expect = set(range(0, 12))
+    expect.remove(10)
+    self.assertEquals(expect, results)
+
+  def testAdd(self):
+    results = set()
+    pool = Pool(3)
+    for result in pool.imap_unordered(Run, [[x] for x in range(0, 10)]):
+      results.add(result)
+      if result < 30:
+        pool.add([result + 20])
+    self.assertEquals(set(range(0, 10) + range(20, 30) + range(40, 50)),
+                      results)