Adds a flag to the standalone vm to throw an exception on 53-bit integer overflow.

runtime/vm/flow_graph_compiler_ia32.cc

Index: runtime/vm/flow_graph_compiler_ia32.cc
===================================================================
--- runtime/vm/flow_graph_compiler_ia32.cc	(revision 23032)
+++ runtime/vm/flow_graph_compiler_ia32.cc	(working copy)
@@ -28,6 +28,7 @@
 DECLARE_FLAG(bool, print_scopes);
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(bool, eliminate_type_checks);
+DECLARE_FLAG(bool, throw_on_53bit_overflow);
 
 
 FlowGraphCompiler::~FlowGraphCompiler() {
@@ -42,7 +43,8 @@
 
 bool FlowGraphCompiler::SupportsUnboxedMints() {
   // Support unboxed mints when SSE 4.1 is available.
-  return FLAG_unbox_mints && CPUFeatures::sse4_1_supported();
+  return FLAG_unbox_mints && CPUFeatures::sse4_1_supported() &&
+         !FLAG_throw_on_53bit_overflow;
 }