Remove RendererDataMemoizingStore which isn't used anymore after r417444.

BUG=504347

Review-Url: https://codereview.chromium.org/2334813002
Cr-Commit-Position: refs/heads/master@{#417989}

content/browser/BUILD.gn

@@ -929,7 +929,6 @@ source_set("browser") {
     "push_messaging/push_messaging_router.h",
     "quota_dispatcher_host.cc",
     "quota_dispatcher_host.h",
-    "renderer_data_memoizing_store.h",
     "renderer_host/clipboard_message_filter.cc",
     "renderer_host/clipboard_message_filter.h",
     "renderer_host/clipboard_message_filter_mac.mm",

content/browser/renderer_data_memoizing_store.h

-// Copyright 2013 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 CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_
-#define CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_
-
-#include <map>
-
-#include "base/bind.h"
-#include "base/synchronization/lock.h"
-#include "content/public/browser/browser_thread.h"
-#include "content/public/browser/render_process_host.h"
-#include "content/public/browser/render_process_host_observer.h"
-
-namespace content {
-
-// RendererDataMemoizingStore is a thread-safe container that retains reference
-// counted objects that are associated with one or more render processes.
-// Objects are identified by an int and only a single reference to a given
-// object is retained. RendererDataMemoizingStore watches for render process
-// termination and releases objects that are no longer associated with any
-// render process.
-//
-// TODO(jcampan): Rather than watching for render process termination, we should
-//                instead be listening to events such as resource cached/
-//                removed from cache, and remove the items when we know they
-//                are not used anymore.
-template <typename T>
-class RendererDataMemoizingStore : public RenderProcessHostObserver {
- public:
-  RendererDataMemoizingStore() : next_item_id_(1) {
-  }
-
-  ~RendererDataMemoizingStore() {
-    DCHECK_EQ(0U, id_to_item_.size()) << "Failed to outlive render processes";
-  }
-
-  // Store adds |item| to this collection, associates it with the given render
-  // process id and returns an opaque identifier for it. If |item| is already
-  // known, the same identifier will be returned.
-  int Store(T* item, int process_id) {
-    DCHECK(item);
-    base::AutoLock auto_lock(lock_);
-
-    int item_id;
-
-    // Do we already know this item?
-    typename ReverseItemMap::iterator item_iter = item_to_id_.find(item);
-    if (item_iter == item_to_id_.end()) {
-      item_id = next_item_id_++;
-      // We use 0 as an invalid item_id value.  In the unlikely event that
-      // next_item_id_ wraps around, we reset it to 1.
-      if (next_item_id_ == 0)
-        next_item_id_ = 1;
-      id_to_item_[item_id] = item;
-      item_to_id_[item] = item_id;
-    } else {
-      item_id = item_iter->second;
-    }
-
-    // Let's update process_id_to_item_id_.
-    std::pair<IDMap::iterator, IDMap::iterator> process_ids =
-        process_id_to_item_id_.equal_range(process_id);
-    bool already_watching_process = (process_ids.first != process_ids.second);
-    if (std::find_if(process_ids.first, process_ids.second,
-                     MatchSecond<int>(item_id)) == process_ids.second) {
-      process_id_to_item_id_.insert(std::make_pair(process_id, item_id));
-    }
-
-    // And item_id_to_process_id_.
-    std::pair<IDMap::iterator, IDMap::iterator> item_ids =
-        item_id_to_process_id_.equal_range(item_id);
-    if (std::find_if(item_ids.first, item_ids.second,
-                     MatchSecond<int>(process_id)) == item_ids.second) {
-      item_id_to_process_id_.insert(std::make_pair(item_id, process_id));
-    }
-
-    // If we're not doing so already, keep an eye for the process host deletion.
-    if (!already_watching_process) {
-      if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
-        StartObservingProcess(process_id);
-      } else {
-        BrowserThread::PostTask(
-            BrowserThread::UI,
-            FROM_HERE,
-            base::Bind(&RendererDataMemoizingStore::StartObservingProcess,
-                       base::Unretained(this),
-                       process_id));
-      }
-    }
-
-    DCHECK(item_id);
-    return item_id;
-  }
-
-  // Retrieve fetches a previously Stored() item, identified by |item_id|.
-  // If |item_id| is recognized, |item| will be updated and Retrieve() will
-  // return true, it will otherwise return false.
-  bool Retrieve(int item_id, scoped_refptr<T>* item) {
-    base::AutoLock auto_lock(lock_);
-
-    typename ItemMap::iterator iter = id_to_item_.find(item_id);
-    if (iter == id_to_item_.end())
-      return false;
-    if (item)
-      *item = iter->second;
-    return true;
-  }
-
- private:
-  typedef std::multimap<int, int> IDMap;
-  typedef std::map<int, scoped_refptr<T> > ItemMap;
-  typedef std::map<T*, int, typename T::LessThan> ReverseItemMap;
-
-  template <typename M>
-  struct MatchSecond {
-    explicit MatchSecond(const M& t) : value(t) {}
-
-    template <typename Pair>
-    bool operator()(const Pair& p) const {
-      return (value == p.second);
-    }
-
-    M value;
-  };
-
-  void StartObservingProcess(int process_id) {
-    DCHECK_CURRENTLY_ON(BrowserThread::UI);
-    RenderProcessHost* host = RenderProcessHost::FromID(process_id);
-    if (!host) {
-      // We lost the race to observe the host before it was destroyed. Since
-      // this function was called because we're managing objects tied to that
-      // (now destroyed) RenderProcessHost, let's clean up.
-      RemoveRenderProcessItems(process_id);
-      return;
-    }
-
-    host->AddObserver(this);
-  }
-
-  // Remove the item specified by |item_id| from id_to_item_ and item_to_id_.
-  // NOTE: the caller (RemoveRenderProcessItems) must hold lock_.
-  void RemoveInternal(int item_id) {
-    typename ItemMap::iterator item_iter = id_to_item_.find(item_id);
-    DCHECK(item_iter != id_to_item_.end());
-
-    typename ReverseItemMap::iterator id_iter =
-        item_to_id_.find(item_iter->second.get());
-    DCHECK(id_iter != item_to_id_.end());
-    item_to_id_.erase(id_iter);
-
-    id_to_item_.erase(item_iter);
-  }
-
-  void RenderProcessHostDestroyed(RenderProcessHost* host) override {
-    DCHECK_CURRENTLY_ON(BrowserThread::UI);
-    RemoveRenderProcessItems(host->GetID());
-  }
-
-  // Removes all the items associated with the specified process from the store.
-  void RemoveRenderProcessItems(int process_id) {
-    base::AutoLock auto_lock(lock_);
-
-    // We iterate through all the item ids for that process.
-    std::pair<IDMap::iterator, IDMap::iterator> process_ids =
-        process_id_to_item_id_.equal_range(process_id);
-    for (IDMap::iterator ids_iter = process_ids.first;
-         ids_iter != process_ids.second; ++ids_iter) {
-      int item_id = ids_iter->second;
-      // Find all the processes referring to this item id in
-      // item_id_to_process_id_, then locate the process being removed within
-      // that range.
-      std::pair<IDMap::iterator, IDMap::iterator> item_ids =
-          item_id_to_process_id_.equal_range(item_id);
-      IDMap::iterator proc_iter = std::find_if(
-          item_ids.first, item_ids.second, MatchSecond<int>(process_id));
-      DCHECK(proc_iter != item_ids.second);
-
-      // Before removing, determine if no other processes refer to the current
-      // item id. If |proc_iter| (the current process) is the lower bound of
-      // processes containing the current item id and if |next_proc_iter| is the
-      // upper bound (the first process that does not), then only one process,
-      // the one being removed, refers to the item id.
-      IDMap::iterator next_proc_iter = proc_iter;
-      ++next_proc_iter;
-      bool last_process_for_item_id =
-          (proc_iter == item_ids.first && next_proc_iter == item_ids.second);
-      item_id_to_process_id_.erase(proc_iter);
-
-      if (last_process_for_item_id) {
-        // The current item id is not referenced by any other processes, so
-        // remove it from id_to_item_ and item_to_id_.
-        RemoveInternal(item_id);
-      }
-    }
-    if (process_ids.first != process_ids.second)
-      process_id_to_item_id_.erase(process_ids.first, process_ids.second);
-  }
-
-  IDMap process_id_to_item_id_;
-  IDMap item_id_to_process_id_;
-  ItemMap id_to_item_;
-  ReverseItemMap item_to_id_;
-
-  int next_item_id_;
-
-  // This lock protects: process_id_to_item_id_, item_id_to_process_id_,
-  //                     id_to_item_, and item_to_id_.
-  base::Lock lock_;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_RENDERER_DATA_MEMOIZING_STORE_H_

content/content_browser.gypi

@@ -1141,7 +1141,6 @@
       'browser/push_messaging/push_messaging_router.h',
       'browser/quota_dispatcher_host.cc',
       'browser/quota_dispatcher_host.h',
-      'browser/renderer_data_memoizing_store.h',
       'browser/renderer_host/clipboard_message_filter.cc',
       'browser/renderer_host/clipboard_message_filter.h',
       'browser/renderer_host/clipboard_message_filter_mac.mm',