Don't optimize away static field initialization when precompiling.

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index 19fe5ad3559b893452e08692b13df6cdfbbb5544..154bf171df786a54bfce0a7e0ef377a59e7a4886 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -51,6 +51,7 @@ DECLARE_FLAG(charp, deoptimize_filter);
 DECLARE_FLAG(bool, disassemble);
 DECLARE_FLAG(bool, disassemble_optimized);
 DECLARE_FLAG(bool, emit_edge_counters);
+DECLARE_FLAG(bool, fields_may_be_reset);
 DECLARE_FLAG(bool, guess_other_cid);
 DECLARE_FLAG(bool, ic_range_profiling);
 DECLARE_FLAG(bool, intrinsify);
@@ -120,6 +121,7 @@ static void PrecompileModeHandler(bool value) {
     FLAG_enable_mirrors = false;
     FLAG_precompile_collect_closures = true;
     FLAG_link_natives_lazily = true;
+    FLAG_fields_may_be_reset = true;
   }
 }