Add -optimize-for-size flag to optimize for memory size

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 479fe2fb6396bc81ac15aebaffb9cb9eae69f16c..ac74604792e47dbd10f9539622246b547807b9de 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1776,10 +1776,6 @@ Isolate::Isolate()
       // TODO(bmeurer) Initialized lazily because it depends on flags; can
       // be fixed once the default isolate cleanup is done.
       random_number_generator_(NULL),
-      // TODO(rmcilroy) Currently setting this based on
-      // FLAG_force_memory_constrained in Isolate::Init; move to here when
-      // isolate cleanup is done
-      is_memory_constrained_(false),
       has_fatal_error_(false),
       use_crankshaft_(true),
       initialized_from_snapshot_(false),
@@ -2138,8 +2134,6 @@ bool Isolate::Init(Deserializer* des) {
   TRACE_ISOLATE(init);
 
   stress_deopt_count_ = FLAG_deopt_every_n_times;
-  if (FLAG_force_memory_constrained.has_value)
-    is_memory_constrained_ = FLAG_force_memory_constrained.value;
 
   has_fatal_error_ = false;