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

src/assembler.h

Index: src/assembler.h
diff --git a/src/assembler.h b/src/assembler.h
index a4c19e6b027bbfdddc97bdec2dd5ab02addce19d..9bfda36499ab5ecd969fab4bf23049297ff143ac 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -101,6 +101,11 @@ class AssemblerBase: public Malloced {
 
   static const int kMinimalBufferSize = 4*KB;
 
+  static void FlushICache(Isolate* isolate, void* start, size_t size);
+
+  // TODO(all): Help get rid of this one.
+  static void FlushICacheWithoutIsolate(void* start, size_t size);
+
  protected:
   // The buffer into which code and relocation info are generated. It could
   // either be owned by the assembler or be provided externally.