[turbofan] Separate JSInliningHeuristic into own class.

src/compiler/js-inlining.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_JS_INLINING_H_
 #define V8_COMPILER_JS_INLINING_H_
 
 #include "src/compiler/js-graph.h"
 #include "src/compiler/graph-reducer.h"
 
 namespace v8 {
 namespace internal {
 
 // Forward declarations.
 class CompilationInfo;
 
 namespace compiler {
 
 // Forward declarations.
 class JSCallFunctionAccessor;
 
+// The JSInliner provides the core graph inlining machinery. Note that this
+// class only deals with the mechanics of how to inline one graph into another,
+// heuristics that decide what and how much to inline are beyond its scope.
 class JSInliner final : public AdvancedReducer {
  public:
-  enum Mode { kRestrictedInlining, kGeneralInlining };
-
-  JSInliner(Editor* editor, Mode mode, Zone* local_zone, CompilationInfo* info,
+  JSInliner(Editor* editor, Zone* local_zone, CompilationInfo* info,
             JSGraph* jsgraph)
       : AdvancedReducer(editor),
-        mode_(mode),
         local_zone_(local_zone),
         info_(info),
         jsgraph_(jsgraph) {}
 
+  // Reducer interface, eagerly inlines everything.
   Reduction Reduce(Node* node) final;
 
+  // Can be used by inlining heuristics or by testing code directly, without
+  // using the above generic reducer interface of the inlining machinery.
+  Reduction ReduceJSCallFunction(Node* node, Handle<JSFunction> function);
+
  private:
-  Mode const mode_;
   Zone* local_zone_;
   CompilationInfo* info_;
   JSGraph* jsgraph_;
 
   Node* CreateArgumentsAdaptorFrameState(JSCallFunctionAccessor* call,
                                          Handle<SharedFunctionInfo> shared_info,
                                          Zone* temp_zone);
 
   Reduction InlineCall(Node* call, Node* context, Node* frame_state,
                        Node* start, Node* end);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_INLINING_H_