Initial design for background compilation

runtime/vm/thread_registry.cc

Index: runtime/vm/thread_registry.cc
diff --git a/runtime/vm/thread_registry.cc b/runtime/vm/thread_registry.cc
index 44c0d133460cd1aa7afda44e1d453d0a9759debe..24445162a5f2bcb5e3cba405bbd84aa758329cd3 100644
--- a/runtime/vm/thread_registry.cc
+++ b/runtime/vm/thread_registry.cc
@@ -4,6 +4,7 @@
 
 #include "vm/thread_registry.h"
 
+#include "vm/compiler.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 
@@ -37,6 +38,11 @@ void ThreadRegistry::SafepointThreads() {
   if (!isolate->MutatorThreadIsCurrentThread()) {
     isolate->ScheduleInterrupts(Isolate::kVMInterrupt);
   }
+  if (isolate->compile_optimized_task() != NULL) {
+    // Make sure the task moves from Wait to a safepoint.

[koda, 2015/10/01 22:27:02]

This should not be needed anymore, now that you enter/exit the isolate in the
loop. I.e., while it's Waiting, the compilation task is not in this isolate, so
will not be included in the rendezvous.

[srdjan, 2015/10/01 23:11:24]

Done.

+    MonitorLocker ml_comp(isolate->compile_optimized_task()->monitor());
+    ml_comp.Notify();
+  }
   while (remaining_ > 0) {
     ml.Wait(Monitor::kNoTimeout);
   }