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

runtime/vm/flow_graph_inliner.cc

Index: runtime/vm/flow_graph_inliner.cc
diff --git a/runtime/vm/flow_graph_inliner.cc b/runtime/vm/flow_graph_inliner.cc
index c01304d3f1ea29d271d5742b2b3ab9353a153a1f..df66eb50065a7b9f150c191846bd30c7bf1760c2 100644
--- a/runtime/vm/flow_graph_inliner.cc
+++ b/runtime/vm/flow_graph_inliner.cc
@@ -4,6 +4,7 @@
 
 #include "vm/flow_graph_inliner.h"
 
+#include "vm/assert.h"
 #include "vm/compiler.h"
 #include "vm/flags.h"
 #include "vm/flow_graph.h"
@@ -145,9 +146,6 @@ class CallSiteInliner : public FlowGraphVisitor {
       caller_graph_->InlineCall(call, callee_graph);
       next_ssa_temp_index_ = caller_graph_->max_virtual_register_number();
 
-      // Check that inlining maintains use lists.
-      DEBUG_ASSERT(caller_graph_->ValidateUseLists());
-
       // Remove push arguments of the call.
       for (intptr_t i = 0; i < call->ArgumentCount(); ++i) {
         PushArgumentInstr* push = call->ArgumentAt(i);
@@ -173,6 +171,9 @@ class CallSiteInliner : public FlowGraphVisitor {
 
       TRACE_INLINING(OS::Print("     Success\n"));
 
+      // Check that inlining maintains use lists.
+      SLOW_ASSERT(caller_graph_->ValidateUseLists());
+
       // Build succeeded so we restore the bailout jump.
       inlined_ = true;
       isolate->set_long_jump_base(base);