Skeleton of the Safe Browsing Subresource Filter.

components/subresource_filter/core/common/activation_state.cc

Index: components/subresource_filter/core/common/activation_state.cc
diff --git a/components/subresource_filter/core/common/activation_state.cc b/components/subresource_filter/core/common/activation_state.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3461eb845f3e1b100cfc62b890d09e7d86655080
--- /dev/null
+++ b/components/subresource_filter/core/common/activation_state.cc
@@ -0,0 +1,31 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/subresource_filter/core/common/activation_state.h"
+
+#include <ostream>
+
+#include "base/logging.h"
+
+namespace subresource_filter {
+
+std::ostream& operator<<(std::ostream& os, const ActivationState& state) {
+  switch (state) {
+    case ActivationState::DISABLED:
+      os << "DISABLED";
+      break;
+    case ActivationState::DRYRUN:
+      os << "DRYRUN";
+      break;
+    case ActivationState::ENABLED:
+      os << "ENABLED";
+      break;
+    default:
+      NOTREACHED();
+      break;

[battre, 2016/05/30 15:29:25]

how about replacing default with LAST? The compiler will complain if a new type
is added to the ActivationState but not to this operator.

[engedy, 2016/05/30 20:54:00]

Could you please elaborate?

[battre, 2016/05/31 08:28:32]

switch(state) {
  case ActivationState::DISABLED: break;
  case ActivationState::DRYRUN: break;
  case ActivationState::ENABLED: break;
  case ActivationState::LAST: break;
}

will generate a compiler error if you add a new value to ActivationState without
updating this switch statement.

Having the default with NOTREACHED is exactly the problem that you encountered
with the devtools. Had they not used default: you would have noticed. Using
default: turns a compile time error into a runtime error.

[engedy, 2016/05/31 08:58:16]

Are you sure we want to depend on non-standardized diagnostic messages offered
by (admittedly most) compilers at various warning levels?

How about instead:

static_assert(ActivationState::ENABLED == ActivationState::LAST, ...);

+  }
+  return os;
+}
+
+}  // namespace subresource_filter