Move CompilerStats from isolate to thread. Aggregate stats.

runtime/vm/atomic_linux.h

Index: runtime/vm/atomic_linux.h
diff --git a/runtime/vm/atomic_linux.h b/runtime/vm/atomic_linux.h
index 15f03965f4255ec751bd26b9bd3587d96e1da717..615004a5647aabfa41f0b6a55d54afa71016a108 100644
--- a/runtime/vm/atomic_linux.h
+++ b/runtime/vm/atomic_linux.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);
 }