Add comments about what should and should not depend on 'allocator'

base/base.gypi

 # Copyright (c) 2012 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.
 
 {
   'target_defaults': {
     'variables': {
       'base_target': 0,
     },
     'target_conditions': [
@@ skipping 89 matching lines @@
           'critical_closure.h',
           'critical_closure_ios.mm',
           'debug/alias.cc',
           'debug/alias.h',
           'debug/debug_on_start_win.cc',
           'debug/debug_on_start_win.h',
           'debug/debugger.cc',
           'debug/debugger.h',
           'debug/debugger_posix.cc',
           'debug/debugger_win.cc',
+          # This file depends on files from the 'allocator' target,
+          # but this target does not depend on 'allocator' (see
+          # allocator.gyp for details).
           'debug/leak_annotations.h',
           'debug/leak_tracker.h',
           'debug/profiler.cc',
           'debug/profiler.h',
           'debug/stack_trace.cc',
           'debug/stack_trace.h',
           'debug/stack_trace_android.cc',
           'debug/stack_trace_ios.mm',
           'debug/stack_trace_posix.cc',
           'debug/stack_trace_win.cc',
@@ skipping 597 matching lines @@
           # Remove all unnecessary files for build_nexe.py to avoid exceeding
           # command-line-string limitation when building NaCl on Windows.
           ['OS == "win" and >(nacl_untrusted_build)==1', {
               'sources/': [ ['exclude', '\\.h$'] ],
           }],
         ],
       }],
     ],
   },
 }