Revert "Don't hide V8 symbols in debug builds"

gni/v8.gni

Index: gni/v8.gni
diff --git a/gni/v8.gni b/gni/v8.gni
index f4ab34bba1bb3e24c69ab2ada06e4cf80f43aab8..9bbc33387681717e4c3370f0953f99006c9fb1e3 100644
--- a/gni/v8.gni
+++ b/gni/v8.gni
@@ -16,9 +16,6 @@ declare_args() {
   # Turns on compiler optimizations in V8 in Debug build.
   v8_optimized_debug = true
 
-  # Support for backtrace_symbols on linux.
-  v8_enable_backtrace = ""
-
   # Enable the snapshot feature, for fast context creation.
   # http://v8project.blogspot.com/2015/09/custom-startup-snapshots.html
   v8_use_snapshot = true
@@ -34,10 +31,6 @@ if (v8_use_external_startup_data == "") {
   v8_use_external_startup_data = v8_use_snapshot && !is_ios
 }
 
-if (v8_enable_backtrace == "") {
-  v8_enable_backtrace = is_debug
-}
-
 ###############################################################################
 # Templates
 #
@@ -70,11 +63,6 @@ if (is_debug && !v8_optimized_debug) {
   }
 }
 
-if (is_posix && v8_enable_backtrace) {
-  v8_remove_configs += [ "//build/config/gcc:symbol_visibility_hidden" ]
-  v8_add_configs += [ "//build/config/gcc:symbol_visibility_default" ]
-}
-
 # All templates should be kept in sync.
 template("v8_source_set") {
   source_set(target_name) {