Remove the dependency of Zone on Isolate

src/compiler/raw-machine-assembler.h

Index: src/compiler/raw-machine-assembler.h
diff --git a/src/compiler/raw-machine-assembler.h b/src/compiler/raw-machine-assembler.h
index 5455814fa206e7e41b6043cf66a230ada384ccb4..7b4644497ea9feb1c85047e0b4be74bc51efa024 100644
--- a/src/compiler/raw-machine-assembler.h
+++ b/src/compiler/raw-machine-assembler.h
@@ -44,13 +44,13 @@ class RawMachineAssembler : public GraphBuilder {
     DISALLOW_COPY_AND_ASSIGN(Label);
   };
 
-  RawMachineAssembler(Graph* graph, MachineSignature* machine_sig,
+  RawMachineAssembler(Isolate* isolate, Graph* graph,
+                      MachineSignature* machine_sig,
                       MachineType word = kMachPtr,
                       MachineOperatorBuilder::Flags flags =
                           MachineOperatorBuilder::Flag::kNoFlags);
   ~RawMachineAssembler() OVERRIDE {}
 
-  Isolate* isolate() const { return zone()->isolate(); }
   Zone* zone() const { return graph()->zone(); }
   MachineOperatorBuilder* machine() { return &machine_; }
   CommonOperatorBuilder* common() { return &common_; }