gn: Remove redundant calls to Scheduler::Increment/DecrementWorkCount().

tools/gn/command_gen.cc

 // Copyright (c) 2013 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.
 
 #include "base/atomicops.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/timer/elapsed_timer.h"
@@ skipping 45 matching lines @@
 // Called on worker thread to write the ninja file.
 void BackgroundDoWrite(TargetWriteInfo* write_info, const Target* target) {
   std::string rule = NinjaTargetWriter::RunAndWriteFile(target);
   DCHECK(!rule.empty());
 
   {
     base::AutoLock lock(write_info->lock);
     write_info->rules[target->toolchain()].emplace_back(
         target, std::move(rule));
   }
-
-  g_scheduler->DecrementWorkCount();
 }
 
 // Called on the main thread.
 void ItemResolvedAndGeneratedCallback(TargetWriteInfo* write_info,
                                       const BuilderRecord* record) {
   const Item* item = record->item();
   const Target* target = item->AsTarget();
   if (target) {
-    g_scheduler->IncrementWorkCount();
     g_scheduler->ScheduleWork(base::Bind(&BackgroundDoWrite,
                                          write_info, target));
   }
 }
 
 // Returns a pointer to the target with the given file as an output, or null
 // if no targets generate the file. This is brute force since this is an
 // error condition and performance shouldn't matter.
 const Target* FindTargetThatGeneratesFile(const Builder& builder,
                                           const SourceFile& file) {
@@ skipping 360 matching lines @@
             setup->scheduler().input_file_manager()->GetInputFileCount()) +
         " files in " +
         base::Int64ToString(elapsed_time.InMilliseconds()) + "ms\n";
     OutputString(stats);
   }
 
   return 0;
 }
 
 }  // namespace commands