linux: TCMalloc-based C++ heap profiler.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index a77a13c0196aa8a1d4b17541731a84bac6e10849..1cc8cca1d1fbf928ff194e1e0feeb683366b471c 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -176,6 +176,9 @@
     # Strip the binary after dumping symbols.
     'linux_strip_binary%': 0,
 
+    # Enable TCMalloc.
+    'linux_use_tcmalloc%': 0,
+
     # Set to select the Title Case versions of strings in GRD files.
     'use_titlecase_in_grd_files%': 0,
 
@@ -709,6 +712,9 @@
               }]
             ],
           }],
+          ['linux_use_tcmalloc==1', {
+            'defines': ['LINUX_USE_TCMALLOC'],
+          }],
         ],
       },
     }],