Introduce the ThrottleManager

components/subresource_filter/content/browser/async_document_subresource_filter.cc

Index: components/subresource_filter/content/browser/async_document_subresource_filter.cc
diff --git a/components/subresource_filter/content/browser/async_document_subresource_filter.cc b/components/subresource_filter/content/browser/async_document_subresource_filter.cc
index 099eec14aae030b3777a73cb64bcdb274ad11387..04aa69a5bfeb7071895e8cf37e71b568d686ec75 100644
--- a/components/subresource_filter/content/browser/async_document_subresource_filter.cc
+++ b/components/subresource_filter/content/browser/async_document_subresource_filter.cc
@@ -58,7 +58,8 @@ AsyncDocumentSubresourceFilter::AsyncDocumentSubresourceFilter(
     : task_runner_(ruleset_handle->task_runner()),
       core_(new Core(), base::OnTaskRunnerDeleter(task_runner_)),
       first_disallowed_load_callback_(
-          std::move(first_disallowed_load_callback)) {
+          std::move(first_disallowed_load_callback)),
+      weak_ptr_factory_(this) {
   DCHECK_NE(ActivationLevel::DISABLED,
             params.parent_activation_state.activation_level);
 
@@ -70,13 +71,22 @@ AsyncDocumentSubresourceFilter::AsyncDocumentSubresourceFilter(
       task_runner_, FROM_HERE,
       base::Bind(&Core::Initialize, base::Unretained(core_.get()),
                  base::Passed(&params), ruleset_handle->ruleset_.get()),
-      std::move(activation_state_callback));
+      base::Bind(&AsyncDocumentSubresourceFilter::OnActivateStateCalculated,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 std::move(activation_state_callback)));
 }
 
 AsyncDocumentSubresourceFilter::~AsyncDocumentSubresourceFilter() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
+void AsyncDocumentSubresourceFilter::OnActivateStateCalculated(
+    base::Callback<void(ActivationState)> activation_state_callback,
+    ActivationState activation_state) {
+  activation_state_.emplace(activation_state);

[engedy, 2017/03/10 17:36:20]

nit: Looks like this is equivalent to:

activation_state_ = activation_state;

WDYT about adopting this convention?

[Charlie Harrison, 2017/03/14 23:18:31]

Done.

+  activation_state_callback.Run(activation_state);
+}
+
 void AsyncDocumentSubresourceFilter::GetLoadPolicyForSubdocument(
     const GURL& subdocument_url,
     LoadPolicyCallback result_callback) {