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

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index 87a76f068821fb3b9982b9955058a27a13d96d91..740cb9b094331e238ab1ee8b61a7d77a0c0b5659 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -622,7 +622,7 @@ void DoubleToIStub::Generate(MacroAssembler* masm) {
 }
 
 
-bool WriteInt32ToHeapNumberStub::IsPregenerated() {
+bool WriteInt32ToHeapNumberStub::IsPregenerated(Isolate* isolate) {
   // These variants are compiled ahead of time.  See next method.
   if (the_int_.is(r1) && the_heap_number_.is(r0) && scratch_.is(r2)) {
     return true;
@@ -2694,8 +2694,8 @@ bool CEntryStub::NeedsImmovableCode() {
 }
 
 
-bool CEntryStub::IsPregenerated() {
-  return (!save_doubles_ || Isolate::Current()->fp_stubs_generated()) &&
+bool CEntryStub::IsPregenerated(Isolate* isolate) {
+  return (!save_doubles_ || isolate->fp_stubs_generated()) &&
           result_size_ == 1;
 }
 
@@ -6457,7 +6457,7 @@ static const AheadOfTimeWriteBarrierStubList kAheadOfTime[] = {
 #undef REG
 
 
-bool RecordWriteStub::IsPregenerated() {
+bool RecordWriteStub::IsPregenerated(Isolate* isolate) {
   for (const AheadOfTimeWriteBarrierStubList* entry = kAheadOfTime;
        !entry->object.is(no_reg);
        entry++) {