Refactor ExternalReference::isolate_address() to not rely on Isolate::Current().

src/arm/regexp-macro-assembler-arm.h

Index: src/arm/regexp-macro-assembler-arm.h
diff --git a/src/arm/regexp-macro-assembler-arm.h b/src/arm/regexp-macro-assembler-arm.h
index c45669ae899f0f709cc4dc3bfa6ab0f71efd57bf..921d8f5474955b28e2a78edaed6d76a7abbaea62 100644
--- a/src/arm/regexp-macro-assembler-arm.h
+++ b/src/arm/regexp-macro-assembler-arm.h
@@ -30,6 +30,7 @@
 
 #include "arm/assembler-arm.h"
 #include "arm/assembler-arm-inl.h"
+#include "macro-assembler.h"
 
 namespace v8 {
 namespace internal {
@@ -223,6 +224,7 @@ class RegExpMacroAssemblerARM: public NativeRegExpMacroAssembler {
   inline void CallCFunctionUsingStub(ExternalReference function,
                                      int num_arguments);
 
+  Isolate* isolate() const { return masm_->isolate(); }
 
   MacroAssembler* masm_;