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

src/x64/assembler-x64-inl.h

Index: src/x64/assembler-x64-inl.h
diff --git a/src/x64/assembler-x64-inl.h b/src/x64/assembler-x64-inl.h
index 826c06e5bad61b0ea1bdde583d51b90992e4376e..07d07033e9546b1b6a6b5086c6817532a8598d10 100644
--- a/src/x64/assembler-x64-inl.h
+++ b/src/x64/assembler-x64-inl.h
@@ -448,7 +448,7 @@ Object** RelocInfo::call_object_address() {
 }
 
 
-void RelocInfo::Visit(ObjectVisitor* visitor) {
+void RelocInfo::Visit(Isolate* isolate, ObjectVisitor* visitor) {
   RelocInfo::Mode mode = rmode();
   if (mode == RelocInfo::EMBEDDED_OBJECT) {
     visitor->VisitEmbeddedPointer(this);
@@ -463,12 +463,11 @@ void RelocInfo::Visit(ObjectVisitor* visitor) {
   } else if (RelocInfo::IsCodeAgeSequence(mode)) {
     visitor->VisitCodeAgeSequence(this);
 #ifdef ENABLE_DEBUGGER_SUPPORT
-  // TODO(isolates): Get a cached isolate below.
   } else if (((RelocInfo::IsJSReturn(mode) &&
               IsPatchedReturnSequence()) ||
              (RelocInfo::IsDebugBreakSlot(mode) &&
               IsPatchedDebugBreakSlotSequence())) &&
-             Isolate::Current()->debug()->has_break_points()) {
+             isolate->debug()->has_break_points()) {
     visitor->VisitDebugTarget(this);
 #endif
   } else if (RelocInfo::IsRuntimeEntry(mode)) {