Add _android files for building DartVM on Android

runtime/platform/thread_android.cc

Index: runtime/platform/thread_android.cc
diff --git a/runtime/platform/thread_linux.cc b/runtime/platform/thread_android.cc
similarity index 97%
copy from runtime/platform/thread_linux.cc
copy to runtime/platform/thread_android.cc
index 30e8dcdb34272374b954a7cb08138d3230d51ce4..51e6561d0eba67337309fb2ed2f747384e270d24 100644
--- a/runtime/platform/thread_linux.cc
+++ b/runtime/platform/thread_android.cc
@@ -211,9 +211,6 @@ Monitor::Monitor() {
   result = pthread_condattr_init(&cond_attr);
   VALIDATE_PTHREAD_RESULT(result);
 
-  result = pthread_condattr_setclock(&cond_attr, CLOCK_MONOTONIC);
-  VALIDATE_PTHREAD_RESULT(result);
-
   result = pthread_cond_init(data_.cond(), &cond_attr);
   VALIDATE_PTHREAD_RESULT(result);
 
@@ -255,7 +252,8 @@ Monitor::WaitResult Monitor::Wait(int64_t millis) {
   } else {
     struct timespec ts;
     ComputeTimeSpec(&ts, millis);
-    int result = pthread_cond_timedwait(data_.cond(), data_.mutex(), &ts);
+    int result = pthread_cond_timedwait_monotonic(
+        data_.cond(), data_.mutex(), &ts);
     ASSERT((result == 0) || (result == ETIMEDOUT));
     if (result == ETIMEDOUT) {
       retval = kTimedOut;