Enable TCMalloc on Linux by default.

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index ca7182981291f5ca1eb51e47a5f2b5ddf66ea20f..37aff2d0b8bd071d6fa5afd8c5d428c29c6cc132 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -385,30 +385,12 @@
         [ 'OS == "linux" or OS == "freebsd"', {
             'sources/': [ ['exclude', '_(mac|win|chromeos)\\.cc$'],
                           ['exclude', '\\.mm?$' ] ],
-            'variables' : {
-              'linux_use_heapchecker%' : 0,
-            },
             'conditions': [
               [ 'chromeos==1 or toolkit_views==1', {
                   'sources/': [ ['include', '_chromeos\\.cc$'] ]
                 },
               ],
-              [ 'linux_use_heapchecker==1', {
-                  'defines': [
-                    'LINUX_USE_HEAPCHECKER',
-                  ],
-                  'direct_dependent_settings': {
-                    'defines': [
-                      'LINUX_USE_HEAPCHECKER',
-                    ],
-                  },
-                },
-              ],
-              # linux_use_heapchecker==1 implies linux_use_tcmalloc=1.
-              [ 'linux_use_tcmalloc==1 or linux_use_heapchecker==1', {
-                  'dependencies': [
-                    '../third_party/tcmalloc/tcmalloc.gyp:tcmalloc',
-                  ],
+              [ 'linux_use_tcmalloc==1', {
                   'defines': [
                     'LINUX_USE_TCMALLOC',
                   ],
@@ -692,6 +674,14 @@
             'file_version_info_unittest.cc',
             'worker_pool_linux_unittest.cc',
           ],
+          'conditions': [
+            [ 'linux_use_tcmalloc==1', {
+                'dependencies': [
+                  '../third_party/tcmalloc/tcmalloc.gyp:tcmalloc',
+                ],
+              },
+            ],
+          ],
           'dependencies': [
             '../build/linux/system.gyp:gtk',
             '../build/linux/system.gyp:nss',