Fix multi-isolate build:

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index af0067cc38bc3792ecc36504f8c115967830531c..40554980ede4ca5c83ffb7d85c4199b044713e44 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -41,11 +41,14 @@ namespace internal {
 // -------------------------------------------------------------------------
 // MacroAssembler implementation.
 
-MacroAssembler::MacroAssembler(void* buffer, int size)
-    : Assembler(Isolate::Current(), buffer, size),
+MacroAssembler::MacroAssembler(Isolate* arg_isolate, void* buffer, int size)
+    : Assembler(arg_isolate, buffer, size),
       generating_stub_(false),
-      allow_stub_calls_(true),
-      code_object_(isolate()->heap()->undefined_value()) {
+      allow_stub_calls_(true) {
+  if (isolate() != NULL) {
+    code_object_ = Handle<Object>(isolate()->heap()->undefined_value(),
+                                  isolate());
+  }
 }
 
 
@@ -2028,7 +2031,9 @@ void MacroAssembler::CallCFunction(Register function,
 
 
 CodePatcher::CodePatcher(byte* address, int size)
-    : address_(address), size_(size), masm_(address, size + Assembler::kGap) {
+    : address_(address),
+      size_(size),
+      masm_(Isolate::Current(), address, size + Assembler::kGap) {
   // Create a new macro assembler pointing to the address of the code to patch.
   // The size is adjusted with kGap on order for the assembler to generate size
   // bytes of instructions without failing with buffer size constraints.