Use a direct include of strings headers in testing/, third_party/, tools/.

tools/memory_watcher/memory_watcher.cc

 // Copyright (c) 2010 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 <algorithm>
 #include <windows.h>
 #include <tlhelp32.h>     // for CreateToolhelp32Snapshot()
 #include <map>
 
 #include "tools/memory_watcher/memory_watcher.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/metrics/stats_counters.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/lock.h"
 #include "tools/memory_watcher/call_stack.h"
 #include "tools/memory_watcher/preamble_patcher.h"
 
 static base::StatsCounter mem_in_use("MemoryInUse.Bytes");
 static base::StatsCounter mem_in_use_blocks("MemoryInUse.Blocks");
 static base::StatsCounter mem_in_use_allocs("MemoryInUse.Allocs");
 static base::StatsCounter mem_in_use_frees("MemoryInUse.Frees");
 
@@ skipping 221 matching lines @@
     CallStack* stack = stack_track->stack;
     PrivateAllocatorString output;
     stack->ToString(&output);
     fprintf(file_, "%s", output.c_str());
   }
   fprintf(file_, "Total Leaks:  %d\n", total_blocks);
   fprintf(file_, "Total Stacks: %d\n", stack_tracks.size());
   fprintf(file_, "Total Bytes:  %d\n", total_bytes);
   CloseLogFile();
 }