MIPS: remove most uses of Isolate::Current in arch specific files.

src/mips/regexp-macro-assembler-mips.cc

Index: src/mips/regexp-macro-assembler-mips.cc
diff --git a/src/mips/regexp-macro-assembler-mips.cc b/src/mips/regexp-macro-assembler-mips.cc
index 7b67a7b47f98b2db15e5b528863476d182ba726e..1a04fd10292b2532256bcecc315ff4ecadf263b5 100644
--- a/src/mips/regexp-macro-assembler-mips.cc
+++ b/src/mips/regexp-macro-assembler-mips.cc
@@ -882,7 +882,7 @@ Handle<HeapObject> RegExpMacroAssemblerMIPS::GetCode(Handle<String> source) {
   masm_->GetCode(&code_desc);
   Handle<Code> code = isolate()->factory()->NewCode(
       code_desc, Code::ComputeFlags(Code::REGEXP), masm_->CodeObject());
-  LOG(Isolate::Current(), RegExpCodeCreateEvent(*code, *source));
+  LOG(masm_->isolate(), RegExpCodeCreateEvent(*code, *source));
   return Handle<HeapObject>::cast(code);
 }
 
@@ -1086,7 +1086,6 @@ int RegExpMacroAssemblerMIPS::CheckStackGuardState(Address* return_address,
                                                    Code* re_code,
                                                    Address re_frame) {
   Isolate* isolate = frame_entry<Isolate*>(re_frame, kIsolate);
-  ASSERT(isolate == Isolate::Current());
   if (isolate->stack_guard()->IsStackOverflow()) {
     isolate->StackOverflow();
     return EXCEPTION;