Megamorphic code cleanup.

runtime/vm/flow_graph_compiler_arm.cc

Index: runtime/vm/flow_graph_compiler_arm.cc
diff --git a/runtime/vm/flow_graph_compiler_arm.cc b/runtime/vm/flow_graph_compiler_arm.cc
index 66465fc80e1b4386d69322c4051002ecc3390466..7c3334c479eaf733d10d28a41f90e40768f0c179 100644
--- a/runtime/vm/flow_graph_compiler_arm.cc
+++ b/runtime/vm/flow_graph_compiler_arm.cc
@@ -27,7 +27,6 @@ DEFINE_FLAG(bool, trap_on_deoptimization, false, "Trap on deoptimization.");
 DEFINE_FLAG(bool, unbox_mints, true, "Optimize 64-bit integer arithmetic.");
 DEFINE_FLAG(bool, unbox_doubles, true, "Optimize double arithmetic.");
 DECLARE_FLAG(bool, enable_simd_inline);
-DECLARE_FLAG(bool, use_megamorphic_stub);
 
 
 void MegamorphicSlowPath::EmitNativeCode(FlowGraphCompiler* compiler) {
@@ -1342,12 +1341,8 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
     __ Comment("Slow case: megamorphic call");
   }
   __ LoadObject(R9, cache);
-  if (FLAG_use_megamorphic_stub) {
-    __ ldr(LR, Address(THR, Thread::megamorphic_lookup_entry_point_offset()));
-    __ blx(LR);
-  } else {
-    StubCode::EmitMegamorphicLookup(assembler());
-  }
+  __ ldr(LR, Address(THR, Thread::megamorphic_lookup_entry_point_offset()));
+  __ blx(LR);
   __ blx(R1);
 
   __ Bind(&done);