[turbofan] add ForTesting to pipeline entry points that are for testing only.

test/cctest/compiler/function-tester.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_CCTEST_COMPILER_FUNCTION_TESTER_H_
 #define V8_CCTEST_COMPILER_FUNCTION_TESTER_H_
 
 #include "src/v8.h"
 #include "test/cctest/cctest.h"
 
@@ skipping 198 matching lines @@
   Handle<JSFunction> CompileGraph(Graph* graph) {
     CHECK(Pipeline::SupportedTarget());
     CompilationInfoWithZone info(function);
 
     CHECK(Parser::Parse(&info));
     info.SetOptimizing(BailoutId::None(),
                        Handle<Code>(function->shared()->code()));
     CHECK(Compiler::Analyze(&info));
     CHECK(Compiler::EnsureDeoptimizationSupport(&info));
 
-    Pipeline pipeline(&info);
-    Linkage linkage(info.zone(), &info);
-    Handle<Code> code = pipeline.GenerateCodeForMachineGraph(&linkage, graph);
+    Handle<Code> code = Pipeline::GenerateCodeForTesting(&info, graph);
     CHECK(!code.is_null());
     function->ReplaceCode(*code);
     return function;
   }
 };
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_CCTEST_COMPILER_FUNCTION_TESTER_H_