Add use_allocator instead of linux_use_tcmalloc to switch the allocator.

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index fe1b0e09ac73b3d38818e9b61565b7a54b95d1dd..fad9974a743d248d06a3de59fee3068367caa3a6 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -1026,7 +1026,8 @@
             ['exclude', 'display/resolution_notification_controller_unittest.cc'],
           ],
         }],
-        ['OS=="linux" and component=="shared_library" and linux_use_tcmalloc==1', {
+        # TODO(dmikurube): Kill linux_use_tcmalloc. http://crbug.com/345554

[darin (slow to review), 2014/03/01 00:38:56]

maybe this GYP block would be better as a .gypi that other can include? there is
a lot of duplication of this snippet across the codebase.

[Dai Mikurube (NOT FULLTIME), 2014/03/01 01:01:19]

Sure. Maybe. But actually, it's not trivial since they have some differences per
platform and/or other conditions. I and primiano@ plan a gyp refactoring later
(discussed in the bug), but we need use_allocator earlier.

+        ['OS=="linux" and component=="shared_library" and ((use_allocator!="none" and use_allocator!="see_use_tcmalloc") or (use_allocator=="see_use_tcmalloc" and linux_use_tcmalloc==1))', {
           'dependencies': [
             '<(DEPTH)/base/allocator/allocator.gyp:allocator',
           ],