Fix occasional deadlock caused by checkpoint root marking.

There was a race where a new worker thread would attach during the
checkpoint. This caused the thread to wait since suspend count != 0.
But when we decremented the suspend count, we did not broadcast to
the resume condition.

Added a create peer parameter to Thread::Attach and
AttachCurrentThread. This is used by the threadpool since we don't
need a java peer for worker threads.

Change-Id: I632926b5a6b52eeb0684b6e1dcbf3db42ba3d35c
diff --git a/src/signal_catcher.cc b/src/signal_catcher.cc
index b54c819..db0d2c7 100644
--- a/src/signal_catcher.cc
+++ b/src/signal_catcher.cc
@@ -186,7 +186,8 @@
   CHECK(signal_catcher != NULL);
 
   Runtime* runtime = Runtime::Current();
-  CHECK(runtime->AttachCurrentThread("Signal Catcher", true, runtime->GetSystemThreadGroup()));
+  CHECK(runtime->AttachCurrentThread("Signal Catcher", true, runtime->GetSystemThreadGroup(),
+                                     !runtime->IsCompiler()));
 
   Thread* self = Thread::Current();
   DCHECK_NE(self->GetState(), kRunnable);