Update Linux build docs to remove GYP references.

docs/linux_debugging.md

Index: docs/linux_debugging.md
diff --git a/docs/linux_debugging.md b/docs/linux_debugging.md
index 058391db0025c2e6107d733d56138e06200232aa..5aa7357f91377da9452e71fc0847793c3e98dead 100644
--- a/docs/linux_debugging.md
+++ b/docs/linux_debugging.md
@@ -271,7 +271,7 @@ for more info.
 
 You can improve GDB load time significantly at the cost of link time by
 plitting symbols from the object files. In GN, set `use_debug_fission=false` in

[Dirk Pranke, 2016/04/11 21:51:07]

nit: typo s/plitting/splitting/.

-your "gn args". In GYP add `linux_use_debug_fission=0` to your `GYP_DEFINES`.
+your "gn args".
 
 ## Core files
 
@@ -428,10 +428,9 @@ some instances in webkit that are ignorable. On systems with prelink and address
 space randomization (e.g. Fedora), you may also see valgrind errors in libstdc++
 on startup and in gnome-breakpad.
 
-Valgrind doesn't seem to play nice with tcmalloc. To disable tcmalloc run GYP
+Valgrind doesn't seem to play nice with tcmalloc. To disable tcmalloc set the GN arg:
 
-    $ cd $CHROMIUM_ROOT/src
-    $ build/gyp_chromium -Duse_allocator=none
+    use_allocator="none"
 
 and rebuild.