Move CompilerStats from isolate to thread. Aggregate stats.

runtime/vm/atomic_macos.h

Index: runtime/vm/atomic_macos.h
diff --git a/runtime/vm/atomic_macos.h b/runtime/vm/atomic_macos.h
index fd5af872c3f58e438424af42e4c78a70ddee7a8e..ae5da3ada6ac43fe71462114cadb2de31e955225 100644
--- a/runtime/vm/atomic_macos.h
+++ b/runtime/vm/atomic_macos.h
@@ -26,6 +26,11 @@ inline void AtomicOperations::IncrementBy(intptr_t* p, intptr_t value) {
 }
 
 
+inline void AtomicOperations::IncrementInt64By(int64_t* p, int64_t value) {
+  __sync_fetch_and_add(p, value);
+}
+
+
 inline uintptr_t AtomicOperations::FetchAndDecrement(uintptr_t* p) {
   return __sync_fetch_and_sub(p, 1);
 }