Reland of land #2 of Enable whitelist generation for official builds.

tools/grit/grit_rule.gni

Index: tools/grit/grit_rule.gni
diff --git a/tools/grit/grit_rule.gni b/tools/grit/grit_rule.gni
index d314e9b82a60b00c8e3fff8b22e12dd84e0410e4..d1207ad63e5f0eb641a95686d8681779834d7bb9 100644
--- a/tools/grit/grit_rule.gni
+++ b/tools/grit/grit_rule.gni
@@ -85,9 +85,13 @@
 import("//third_party/closure_compiler/closure_args.gni")
 
 declare_args() {
-  # Enables used resource whitelist generation.
-  enable_resource_whitelist_generation = false
-}
+  # Enables used resource whitelist generation. Set for official builds only
+  # as a large amount of build output is generated.
+  enable_resource_whitelist_generation = is_android && is_official_build
+}
+
+assert(!enable_resource_whitelist_generation || is_android,
+       "resource whitelist generation only works on android")
 
 grit_defines = []