[compiler] Make OptimizedCompileJob agnostic from backend.

src/crankshaft/hydrogen.h

Index: src/crankshaft/hydrogen.h
diff --git a/src/crankshaft/hydrogen.h b/src/crankshaft/hydrogen.h
index 1475374d83537dc04478215ec1e6c59d1e728651..30700bf41b17baa46065ee85f81b815ec909dbf7 100644
--- a/src/crankshaft/hydrogen.h
+++ b/src/crankshaft/hydrogen.h
@@ -30,6 +30,20 @@ class LAllocator;
 class LChunk;
 class LiveRange;
 
+class HCompilationJob final : public OptimizedCompileJob {
+ public:
+  explicit HCompilationJob(CompilationInfo* info)
+      : OptimizedCompileJob(info), graph_(nullptr), chunk_(nullptr) {}
+
+ protected:
+  virtual Status CreateGraphImpl();
+  virtual Status OptimizeGraphImpl();
+  virtual Status GenerateCodeImpl();
+
+ private:
+  HGraph* graph_;
+  LChunk* chunk_;
+};
 
 class HBasicBlock final : public ZoneObject {
  public: