[turbofan] Move graph trimming functionality to dedicated GraphTrimmer.

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/mips.gni")
 
 # Because standalone V8 builds are not supported, assume this is part of a
 # Chromium build.
@@ skipping 624 matching lines @@
     "src/compiler/frame-elider.h",
     "src/compiler/frame-states.cc",
     "src/compiler/frame-states.h",
     "src/compiler/gap-resolver.cc",
     "src/compiler/gap-resolver.h",
     "src/compiler/graph-builder.h",
     "src/compiler/graph-reducer.cc",
     "src/compiler/graph-reducer.h",
     "src/compiler/graph-replay.cc",
     "src/compiler/graph-replay.h",
+    "src/compiler/graph-trimmer.cc",
+    "src/compiler/graph-trimmer.h",
     "src/compiler/graph-visualizer.cc",
     "src/compiler/graph-visualizer.h",
     "src/compiler/graph.cc",
     "src/compiler/graph.h",
     "src/compiler/greedy-allocator.cc",
     "src/compiler/greedy-allocator.h",
     "src/compiler/instruction-codes.h",
     "src/compiler/instruction-selector-impl.h",
     "src/compiler/instruction-selector.cc",
     "src/compiler/instruction-selector.h",
@@ skipping 1024 matching lines @@
       sources += [
         "src/d8-debug.cc",
         "$target_gen_dir/d8-js.cc",
       ]
     }
     if (v8_enable_i18n_support) {
       deps += [ "//third_party/icu" ]
     }
   }
 }