base/allocator: Hardcode TCMalloc debug optimization level to 2 on Linux.

base/allocator/allocator.gyp

Index: base/allocator/allocator.gyp
diff --git a/base/allocator/allocator.gyp b/base/allocator/allocator.gyp
index 2de3aca450f939efc78037a4a28f5b000c2829e7..d76a31f4cf010fb7ec58c12a084ec8c1794757ef 100644
--- a/base/allocator/allocator.gyp
+++ b/base/allocator/allocator.gyp
@@ -306,6 +306,9 @@
             # e.g. for profiling (it's more rare to profile Debug builds,
             # but people sometimes need to do that).
             'disable_debugallocation%': 0,
+            # This code gets run a lot and debugged rarely, so it should be fast
+            # by default. See http://crbug.com/388949.
+            'debug_optimize': 2,
           },
           'conditions': [
             # TODO(phajdan.jr): Also enable on Windows.