[base/allocator] Fix TCMalloc exclusion in allocator.gni.

The build file wants to exclude TCMalloc, but it also excludes
PartitionAlloc. This is incompatible with PartitionAlloc everywhere.

Bug: 998048
Change-Id: I5c234c70bd0e3b73d69fd8e648ac36be1510d872
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377710Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801767}

base/allocator/allocator.gni

@@ -45,9 +45,11 @@ assert(use_allocator == "none" || use_allocator == "tcmalloc" ||
 # Don't ship this configuration, not ready yet.
 assert(!(use_allocator == "partition" && is_official_build))
 
-assert(!is_win || use_allocator == "none", "Tcmalloc doesn't work on Windows.")
-assert(!is_mac || use_allocator == "none", "Tcmalloc doesn't work on macOS.")
-assert(!is_ios || use_allocator == "none", "Tcmalloc doesn't work on iOS.")
+assert(!is_win || use_allocator != "tcmalloc",
+       "Tcmalloc doesn't work on Windows.")
+assert(!is_mac || use_allocator != "tcmalloc",
+       "Tcmalloc doesn't work on macOS.")
+assert(!is_ios || use_allocator != "tcmalloc", "Tcmalloc doesn't work on iOS.")
 
 assert(
     !use_allocator_shim || is_linux || is_chromeos || is_android || is_win ||