Created placeholders for MallocHooks implementation and added define DART_USE_TCMALLOC to specifiy …

runtime/bin/bin.gypi

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 {
   'variables': {
     'gen_source_dir': '<(SHARED_INTERMEDIATE_DIR)',
 
     'io_cc_file': '<(gen_source_dir)/io_gen.cc',
     'io_patch_cc_file': '<(gen_source_dir)/io_patch_gen.cc',
@@ skipping 1133 matching lines @@
           'msvs_settings': {
             'VCLinkerTool': {
               'AdditionalOptions': [ '/EXPORT:Dart_True' ],
             },
           },
         }],
         ['OS == "linux" and asan == 0 and msan == 0 and tsan == 0', {
           'dependencies': [
             '../third_party/tcmalloc/tcmalloc.gypi:tcmalloc',
           ],
+          'defines': [
+            'DART_USE_TCMALLOC'
+          ],
         }],
       ],
       'configurations': {
         'Dart_Linux_Base': {
           # Have the linker add all symbols to the dynamic symbol table
           # so that extensions can look them up dynamically in the binary.
           'ldflags': [
             '-rdynamic',
           ],
         },
@@ skipping 231 matching lines @@
       'conditions': [
         ['OS=="win"', {
           'link_settings': {
             'libraries': [ '-lws2_32.lib', '-lRpcrt4.lib', '-lwinmm.lib' ],
           },
         }],
         ['OS == "linux" and asan == 0 and msan == 0 and tsan == 0', {
           'dependencies': [
             '../third_party/tcmalloc/tcmalloc.gypi:tcmalloc',
           ],
+          'defines': [
+            'DART_USE_TCMALLOC'
+          ],
         }],
       ],
       'configurations': {
         'Dart_Linux_Base': {
           # Have the linker add all symbols to the dynamic symbol table
           # so that extensions can look them up dynamically in the binary.
           'ldflags': [
             '-rdynamic',
           ],
         },
@@ skipping 39 matching lines @@
         }],
         ['OS=="linux"', {
           'cflags': [
             '-fPIC',
           ],
         }],
       ],
     },
   ],
 }