Add support for building the Dart VM for Android OS.

runtime/platform/thread_android.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/thread.h"
 
 #include <errno.h>
 #include <sys/time.h>
 
 #include "platform/assert.h"
@@ skipping 193 matching lines @@
   result = pthread_mutex_init(data_.mutex(), &mutex_attr);
   VALIDATE_PTHREAD_RESULT(result);
 
   result = pthread_mutexattr_destroy(&mutex_attr);
   VALIDATE_PTHREAD_RESULT(result);
 
   pthread_condattr_t cond_attr;
   result = pthread_condattr_init(&cond_attr);
   VALIDATE_PTHREAD_RESULT(result);
 
+#if 0
+  // This API is not available on Android.

[cshapiro, 2012/08/07 20:56:54]

It is, but only through the non-standard name  pthread_cond_timedwait_monotonic.

I think you should remove this code and update the code for Monitor::Wait to use
pthread_cond_timedwait_monotonic.

[jackpal, 2012/08/07 21:43:26]

Done.

   result = pthread_condattr_setclock(&cond_attr, CLOCK_MONOTONIC);
   VALIDATE_PTHREAD_RESULT(result);
+#endif
 
   result = pthread_cond_init(data_.cond(), &cond_attr);
   VALIDATE_PTHREAD_RESULT(result);
 
   result = pthread_condattr_destroy(&cond_attr);
   VALIDATE_PTHREAD_RESULT(result);
 }
 
 
 Monitor::~Monitor() {
@@ skipping 46 matching lines @@
 }
 
 
 void Monitor::NotifyAll() {
   // TODO(iposva): Do we need to track lock owners?
   int result = pthread_cond_broadcast(data_.cond());
   VALIDATE_PTHREAD_RESULT(result);
 }
 
 }  // namespace dart