[turbofan] Refactor js-inlining.cc to use more graph(), jsgraph(), javascript(), common().

BUG=

Review-Url: https://codereview.chromium.org/2211963002
Cr-Commit-Position: refs/heads/master@{#38363}

src/compiler/js-inlining.h

@@ -36,6 +36,8 @@ class JSInliner final : public AdvancedReducer {
   Reduction ReduceJSCall(Node* node, Handle<JSFunction> function);
 
  private:
+  CommonOperatorBuilder* common() const;
+  JSOperatorBuilder* javascript() const;
   Graph* graph() const;
   JSGraph* jsgraph() const { return jsgraph_; }