Create a field trial for Seccomp-BPF on Android.

content/renderer/renderer_main_platform_delegate_android.cc

Index: content/renderer/renderer_main_platform_delegate_android.cc
diff --git a/content/renderer/renderer_main_platform_delegate_android.cc b/content/renderer/renderer_main_platform_delegate_android.cc
index 8ef130375a7f62d9e6a790ef23f415e84985d6df..775dc4dcf068b7c76e109bbc662403a7b4897a4c 100644
--- a/content/renderer/renderer_main_platform_delegate_android.cc
+++ b/content/renderer/renderer_main_platform_delegate_android.cc
@@ -4,17 +4,50 @@
 
 #include "content/renderer/renderer_main_platform_delegate.h"
 
-#include "base/command_line.h"
+#include "base/android/build_info.h"
+#include "base/feature_list.h"
 #include "base/logging.h"
-#include "content/public/common/content_switches.h"
 
 #ifdef USE_SECCOMP_BPF
 #include "content/common/sandbox_linux/android/sandbox_bpf_base_policy_android.h"
+#include "content/public/common/sandbox_init.h"
 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #endif
 
 namespace content {
 
+namespace {
+
+#ifdef USE_SECCOMP_BPF
+// Determines if the running device should support Seccomp, based on the Android
+// SDK version.
+bool IsSeccompBPFSupportedBySDK() {
+  const auto info = base::android::BuildInfo::GetInstance();
+  if (info->sdk_int() < 22) {
+    // Seccomp was never available pre-Lollipop.
+    return false;
+  } else if (info->sdk_int() == 22) {
+    // On Lollipop-MR1, only select Nexus devices have Seccomp available.
+    const char* const kDevices[] = {
+        "deb",   "flo",   "hammerhead", "mako",
+        "manta", "shamu", "sprout",     "volantis",
+    };
+
+    for (const auto& device : kDevices) {
+      if (strcmp(device, info->device()) == 0) {
+        return true;
+      }
+    }
+  } else {
+    // On Marshmallow and higher, Seccomp is required by CTS.
+    return true;
+  }
+  return false;
+}
+#endif  // USE_SECCOMP_BPF
+
+}  // namespace
+
 RendererMainPlatformDelegate::RendererMainPlatformDelegate(
     const MainFunctionParams& parameters)
     : parameters_(parameters) {
@@ -31,20 +64,24 @@ void RendererMainPlatformDelegate::PlatformUninitialize() {
 
 bool RendererMainPlatformDelegate::EnableSandbox() {
 #ifdef USE_SECCOMP_BPF
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableSeccompFilterSandbox)) {
+  // Determine if Seccomp is available via the Android SDK version.
+  if (!IsSeccompBPFSupportedBySDK())
     return true;
-  }
+
+  // Do run-time detection to ensure that support is present.
   if (!sandbox::SandboxBPF::SupportsSeccompSandbox(
           sandbox::SandboxBPF::SeccompLevel::MULTI_THREADED)) {
-    LOG(WARNING) << "Seccomp-BPF sandbox enabled without kernel support. "
-                 << "Ignoring flag and proceeding without seccomp sandbox.";
+    LOG(WARNING) << "Seccomp support should be present, but detection "
+        << "failed. Continuing without Seccomp-BPF.";
     return true;
   }
 
-  sandbox::SandboxBPF sandbox(new SandboxBPFBasePolicyAndroid());
-  CHECK(
-      sandbox.StartSandbox(sandbox::SandboxBPF::SeccompLevel::MULTI_THREADED));
+  // Seccomp has been detected, check if the field trial experiment should run.
+  if (base::FeatureList::IsEnabled(kSeccompSandboxAndroidFeature)) {
+    sandbox::SandboxBPF sandbox(new SandboxBPFBasePolicyAndroid());
+    CHECK(sandbox.StartSandbox(
+        sandbox::SandboxBPF::SeccompLevel::MULTI_THREADED));
+  }
 #endif
   return true;
 }