Make FlushICache part of Assembler(Base) and take Isolate as parameter.

src/x64/code-stubs-x64.h

Index: src/x64/code-stubs-x64.h
diff --git a/src/x64/code-stubs-x64.h b/src/x64/code-stubs-x64.h
index 09289cf3122417ef598af8d3ef2d22761b5984be..2711a072da59bb69d0e41aafedb0bbf1440c63f1 100644
--- a/src/x64/code-stubs-x64.h
+++ b/src/x64/code-stubs-x64.h
@@ -180,7 +180,7 @@ class RecordWriteStub: public PlatformCodeStub {
         break;
     }
     DCHECK(GetMode(stub) == mode);
-    CpuFeatures::FlushICache(stub->instruction_start(), 7);
+    Assembler::FlushICacheWithoutIsolate(stub->instruction_start(), 7);
   }
 
   DEFINE_NULL_CALL_INTERFACE_DESCRIPTOR();