linux: enable seccomp sandbox by default

chrome/renderer/renderer_main_platform_delegate_linux.cc

Index: chrome/renderer/renderer_main_platform_delegate_linux.cc
diff --git a/chrome/renderer/renderer_main_platform_delegate_linux.cc b/chrome/renderer/renderer_main_platform_delegate_linux.cc
index bce15dd964c79fbd54502a09d8c6c928dfeb4d94..2ab392a6e7d7a5cda18519cba6676d8142ead347 100644
--- a/chrome/renderer/renderer_main_platform_delegate_linux.cc
+++ b/chrome/renderer/renderer_main_platform_delegate_linux.cc
@@ -40,9 +40,8 @@ bool RendererMainPlatformDelegate::EnableSandbox() {
   // N.b. SupportsSeccompSandbox() returns a cached result, as we already
   // called it earlier in the zygote. Thus, it is OK for us to not pass in
   // a file descriptor for "/proc".
-  if (CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableSeccompSandbox) &&
-      SupportsSeccompSandbox(-1)) {
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableSeccompSandbox)) {
     StartSeccompSandbox();
   }
 #endif