Added slow_assert macro and flag for slow development assertions in the VM.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index d462881fee0e42a6bd6c5c80b6260677ed23481b..7289a7423ad97cf8232ccecea6c9f72574792c18 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -47,6 +47,7 @@ DEFINE_FLAG(int, deoptimization_counter_threshold, 5,
     " certain optimizations");
 DEFINE_FLAG(bool, use_inlining, true, "Enable call-site inlining");
 DEFINE_FLAG(bool, range_analysis, true, "Enable range analysis");
+DEFINE_FLAG(bool, slow_assert, false, "Enable slow assertions");
 DECLARE_FLAG(bool, print_flow_graph);
 
 
@@ -180,8 +181,6 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
         if (FLAG_use_inlining) {
           FlowGraphInliner inliner(flow_graph);
           inliner.Inline();
-          // Verify that the use lists are still valid.
-          DEBUG_ASSERT(flow_graph->ValidateUseLists());
         }
 
         // Propagate types and eliminate more type tests.
@@ -191,7 +190,7 @@ static bool CompileParsedFunctionHelper(const ParsedFunction& parsed_function,
         }
 
         // Verify that the use lists are still valid.
-        DEBUG_ASSERT(flow_graph->ValidateUseLists());
+        SLOW_ASSERT(flow_graph->ValidateUseLists());
 
         // Propagate sminess from CheckSmi to phis.
         optimizer.PropagateSminess();