Remove "nacl_defines" from the GN build.

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 438728f6b26a0411622b39e27bb136692cdbd064..3d1dfe794620f40536530980f1ba489dd20deb2f 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -5,7 +5,6 @@
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
-import("//components/nacl/nacl_defines.gni")
 
 # //build/config/android/rules.gni imports //tools/grit/grit_rule.gni, which
 # produces a conflict for the "grit" template so we have to only include one.
@@ -232,8 +231,6 @@ static_library("browser") {
     #        # chrome/browser/metrics/variations/generate_resources_map.py
     #        '<(SHARED_INTERMEDIATE_DIR)/chrome/browser/metrics/variations/generated_resources_map.cc',
 
-    defines = nacl_defines
-
     deps += [
       "//apps",
       "//cc",