Introduce the ThrottleManager

components/subresource_filter/content/browser/content_subresource_filter_throttle_manager.h

+// 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_CONTENT_SUBRESOURCE_FILTER_THROTTLE_MANAGER_H_
+#define COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_CONTENT_SUBRESOURCE_FILTER_THROTTLE_MANAGER_H_
+
+#include <memory>
+#include <unordered_map>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "components/subresource_filter/content/browser/verified_ruleset_dealer.h"
+#include "components/subresource_filter/core/common/activation_state.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace content {
+class NavigationHandle;
+class NavigationThrottle;
+class RenderFrameHost;
+}  // namespace content
+
+namespace subresource_filter {
+
+class AsyncDocumentSubresourceFilter;
+class ActivationStateComputingNavigationThrottle;
+
+// Simple struct which contains useful information regarding a frame's
+// activation. This includes its DocumentSubresourceFilter, as well as its
+// ActivationState.
+struct FrameActivationInfo {
+  FrameActivationInfo();
+  ~FrameActivationInfo();
+  std::unique_ptr<AsyncDocumentSubresourceFilter> subresource_filter;
+  ActivationState activation_state;
+};
+
+using ActivatedFrameHostMap =

[engedy, 2017/02/17 15:34:27]

nit: We should at least move this down to the `private:` section inside the
class. We might potentially get rid of the type aliases altogether, I think the
underlying type names are more meaningful.

[Charlie Harrison, 2017/02/17 18:04:35]

Got rid of them.

+    std::unordered_map<content::RenderFrameHost*,
+                       std::unique_ptr<FrameActivationInfo>>;
+using OngoingActivationThrottleMap =
+    std::unordered_map<content::NavigationHandle*,
+                       ActivationStateComputingNavigationThrottle*>;
+
+class ContentSubresourceFilterThrottleManager
+    : public content::WebContentsObserver {
+ public:
+  // It is expected that the Delegate outlives |this|, and manages the lifetime
+  // of this class.
+  class Delegate : public base::SupportsWeakPtr<Delegate> {
+   public:
+    virtual VerifiedRulesetDealer::Handle* GetRulesetDealerHandle() = 0;
+
+    // The embedder may be interested in displaying UI to the user when the
+    // first load is disallowed.

[engedy, 2017/02/17 15:34:27]

nit: ... for a given page load.

[Charlie Harrison, 2017/02/17 18:04:35]

Done.

+    virtual void OnFirstSubresourceLoadDisallowed() {}
+
+    // Instruct the delegate to send an IPC to the renderer informing it of
+    // activation.
+    virtual void OnActivationStateComputedForCommittingLoad(
+        content::NavigationHandle* navigation_handle,
+        const ActivationState& activation_state) {}
+
+    // Let the delegate have the last word when it comes to activation. It might
+    // have a specific whitelist.
+    virtual bool ShouldVetoActivation(
+        content::NavigationHandle* navigation_handle);
+  };
+
+  ContentSubresourceFilterThrottleManager(Delegate* delegate,
+                                          content::WebContents* web_contents);
+  ~ContentSubresourceFilterThrottleManager() override;
+
+  // The subframe navigation filtering throttle must be inserted before the

[engedy, 2017/02/17 15:34:27]

On second thought, does the order really matter here? There aren't any
navigation stages where both of two throttles are activated.

[Charlie Harrison, 2017/02/17 18:04:36]

You're right, I've removed the comment.

+  // activation state computing throttle.
+  std::unique_ptr<content::NavigationThrottle>
+  MaybeCreateSubframeNavigationFilteringThrottle(
+      content::NavigationHandle* navigation_handle);
+  std::unique_ptr<content::NavigationThrottle>
+  MaybeCreateActivationStateComputingThrottle(
+      content::NavigationHandle* navigation_handle);
+
+  // Must be called during a navigation, before the corresponding throttle in
+  // |ongoing_activation_throttles_ ureaches WillProcessResponse.
+  void OnPageStateActivationComputed(
+      content::NavigationHandle* activated_navigation,
+      const ActivationState& state);
+
+  // content::WebContentsObserver:
+  void RenderFrameDeleted(content::RenderFrameHost* frame_host) override;
+  void ReadyToCommitNavigation(
+      content::NavigationHandle* navigation_handle) override;
+  void DidFinishNavigation(
+      content::NavigationHandle* navigation_handle) override;
+
+ private:
+  FrameActivationInfo* GetFrameActivationInfoForChildNavigation(
+      content::NavigationHandle* child_frame_navigation);
+
+  VerifiedRuleset::Handle* EnsureRulesetHandle();
+
+  void OnFirstSubresourceLoadDisallowed();
+
+  // Map of all RenderFrameHosts that are currently activated, and their
+  // associated ActivationState and AsyncDocumentSubresourceFilters.
+  ActivatedFrameHostMap activated_frame_hosts_;
+
+  // Map of all ongoing activation computing throttles. This is needed to

[engedy, 2017/02/17 15:34:27]

Phrasing suggestion:

For each ongoing navigation that requires activation state computation, keeps
track of the throttle that is carrying out that computation, so that the result
can be retrieved when the navigation is ready to commit.

[Charlie Harrison, 2017/02/17 18:04:35]

Done.

+  // populate the activated_frame_hosts_ map when the navigation is ready to
+  // commit.
+  OngoingActivationThrottleMap ongoing_activation_throttles_;
+
+  // Lazily instantiated in EnsureRulesetHandle when the first page level
+  // activation is triggered. Will go away when there are no more activated
+  // RenderFrameHosts (i.e. activated_frame_hosts_ is empty).
+  std::unique_ptr<VerifiedRuleset::Handle> ruleset_handle_;
+
+  // Must outlive this class.
+  Delegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(ContentSubresourceFilterThrottleManager);
+};
+
+}  // namespace subresource_filter
+
+#endif  // COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_CONTENT_SUBRESOURCE_FILTER_THROTTLE_MANAGER_H_