Introduce AsyncDocumentSubresourceFilter.

components/subresource_filter/content/browser/async_document_subresource_filter.h

Index: components/subresource_filter/content/browser/async_document_subresource_filter.h
diff --git a/components/subresource_filter/content/browser/async_document_subresource_filter.h b/components/subresource_filter/content/browser/async_document_subresource_filter.h
new file mode 100644
index 0000000000000000000000000000000000000000..43b4660c738cd48b400c1f3497e98279830c1ce2
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+++ b/components/subresource_filter/content/browser/async_document_subresource_filter.h
@@ -0,0 +1,138 @@
+// Copyright 2017 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.
+
+#ifndef COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_ASYNC_DOCUMENT_SUBRESOURCE_FILTER_H_
+#define COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_ASYNC_DOCUMENT_SUBRESOURCE_FILTER_H_
+
+#include <memory>
+
+#include "base/callback_forward.h"
+#include "base/macros.h"
+#include "base/optional.h"
+#include "base/sequenced_task_runner.h"
+#include "base/threading/thread_checker.h"
+#include "components/subresource_filter/content/browser/verified_ruleset_dealer.h"
+#include "components/subresource_filter/content/common/document_subresource_filter.h"
+#include "components/subresource_filter/core/common/activation_level.h"
+#include "components/subresource_filter/core/common/activation_state.h"
+#include "third_party/WebKit/public/platform/WebDocumentSubresourceFilter.h"
+
+namespace subresource_filter {
+
+// An asynchronous wrapper around DocumentSubresourceFilter.
+//
+// It is accessed on the UI thread and owns an ADSF::Core living on a dedicated
+// sequenced |task_runner|. Provides asynchronous access to the Core, and
+// destroys it asynchronously.
+class AsyncDocumentSubresourceFilter {
+ public:
+  using LoadPolicy = blink::WebDocumentSubresourceFilter::LoadPolicy;
+  using LoadPolicyCallback = base::Callback<void(LoadPolicy)>;
+
+  class Core;
+
+  // Parameters posted to ADSF::Core during its initialization. Needed for
+  // computing ActivationState for a document, and for creating a corresponding
+  // DocumentSubresourceFilter.
+  struct InitializationParams {

[Charlie Harrison, 2017/02/13 14:15:45]

From looking at the members, it is not immediately clear how we should construct
a ADSF for the main frame. Do we let the parent_document_origin be
url::Origin(), should the parent_activation_level be the page activation level?

A comment explicitly addressing main frame ADSFs would be nice.

[pkalinnikov, 2017/02/13 14:22:50]

Quick answer: Your interpretation is right. |parent_activation_state| should
have both bool's false, and |activation_level| set to either ENABLED/DRYRUN if
filtering is activated for the main frame, or DISABLED if not activated. You can
simply use InitializationParams constructor with URL and
|parent_activation_level| as a shortcut.

Will add a comment shortly.

[pkalinnikov, 2017/02/13 14:27:39]

Oh, and don't forget to set the |measure_performance| bit of the
|parent_activation_state| appropriately (see the
ShouldMeasurePerformanceForPageLoad function in content/browser and its usage).
Would you like to have this bit in the shortcut constructor?

[Charlie Harrison, 2017/02/13 14:33:58]

Sure that sounds useful. It seems like the shortcut constructor should not be
missing anything that is required by non-test callers. We probably don't want to
miss setting the measure_perf bool in production code so let's make it almost
impossible to.

[pkalinnikov, 2017/02/13 15:26:49]

Does it look good to you now?

[Charlie Harrison, 2017/02/13 16:00:40]

Yep!

+    InitializationParams();
+
+    explicit InitializationParams(
+        GURL document_url,
+        ActivationLevel parent_activation_level = ActivationLevel::ENABLED);
+
+    ~InitializationParams();
+
+    InitializationParams(InitializationParams&& other);
+    InitializationParams& operator=(InitializationParams&& other);
+
+    // Parameters used to compute ActivationState for the |document| before
+    // creating a DocumentSubresourceFilter.
+    GURL document_url;
+    url::Origin parent_document_origin;
+    ActivationState parent_activation_state;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(InitializationParams);
+  };
+
+  // Creates a Core and initializes it asynchronously on a |task_runner| using
+  // the supplied initialization |params| and a VerifiedRuleset taken from the
+  // |ruleset_handle|. The instance remains owned by |this| object, but lives on
+  // (and is accessed on) the |task_runner|.
+  //
+  // Once the ActivationState for the current frame is calculated, it is
+  // reported back via |activation_state_callback| on the task runner associated
+  // with the current thread. If MemoryMappedRuleset is not present or
+  // malformed, then a default ActivationState is reported (with ActivationLevel
+  // equal to DISABLED).
+  //
+  // The |first_disallowed_load_callback|, if it is non-null, is invoked on the
+  // first ReportDisallowedLoad() call.
+  AsyncDocumentSubresourceFilter(
+      VerifiedRuleset::Handle* ruleset_handle,
+      InitializationParams params,
+      base::Callback<void(ActivationState)> activation_state_callback,
+      base::OnceClosure first_disallowed_load_callback);
+
+  ~AsyncDocumentSubresourceFilter();
+
+  // Computes LoadPolicy on a |task_runner| and returns it back to the calling
+  // thread via |result_callback|. If MemoryMappedRuleset is not present or
+  // malformed, then a LoadPolicy::Allow is returned.
+  void GetLoadPolicyForSubdocument(const GURL& subdocument_url,
+                                   LoadPolicyCallback result_callback);
+
+  // Invokes |first_disallowed_load_callback|, if necessary, and posts a task to
+  // call DocumentSubresourceFilter::reportDisallowedCallback() on the
+  // |task_runner|.
+  void ReportDisallowedLoad();
+
+ private:
+  // Note: Raw pointer, |core_| already holds a reference to |task_runner_|.
+  base::SequencedTaskRunner* task_runner_;
+  std::unique_ptr<Core, base::OnTaskRunnerDeleter> core_;
+  base::OnceClosure first_disallowed_load_callback_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(AsyncDocumentSubresourceFilter);
+};
+
+// Holds a DocumentSubresourceFilter (after Initialization, in case there is a
+// valid MemoryMappedRuleset), and provides access to it.
+//
+// Initially holds an empty filter, allowing this object to be created on the
+// UI thread synchronously, hence letting the ADSF to be created synchronously
+// and be immediately used by clients on the UI thread, while the DSF is
+// retrieved on the |task_runner| in a deferred manner.
+class AsyncDocumentSubresourceFilter::Core {
+ public:
+  Core();
+  ~Core();
+
+  // Can return nullptr even after initialization in case MemoryMappedRuleset
+  // was not present, or was malformed during it.
+  DocumentSubresourceFilter* filter() {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    return filter_ ? &filter_.value() : nullptr;
+  }
+
+ private:
+  friend class AsyncDocumentSubresourceFilter;
+
+  // Computes ActivationState from |params| and initializes a DSF using it.
+  // Returns the computed activation state.
+  ActivationState Initialize(InitializationParams params,
+                             VerifiedRuleset* verified_ruleset);
+
+  base::Optional<DocumentSubresourceFilter> filter_;
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(Core);
+};
+
+}  // namespace subresource_filter
+
+#endif  // COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_ASYNC_DOCUMENT_SUBRESOURCE_FILTER_H_