Adds speculative prefetching of resources.

chrome/browser/predictors/resource_prefetcher_manager.cc

+// Copyright (c) 2012 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 "chrome/browser/predictors/resource_prefetcher_manager.h"
+
+#include "base/bind.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context_getter.h"
+
+using content::BrowserThread;
+
+namespace predictors {
+
+ResourcePrefetcherManager::ResourcePrefetcherManager(
+    Delegate* delegate,
+    const ResourcePrefetchPredictorConfig& config,
+    net::URLRequestContextGetter* context_getter)
+    : delegate_(delegate),
+      config_(config),
+      context_getter_(context_getter) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  CHECK(delegate_);
+  CHECK(context_getter_);
+}
+
+ResourcePrefetcherManager::~ResourcePrefetcherManager() {
+}
+
+void ResourcePrefetcherManager::ShutdownOnUIThread() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  delegate_ = NULL;
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+      base::Bind(&ResourcePrefetcherManager::ShutdownOnIOThread,
+                 this));
+}
+
+void ResourcePrefetcherManager::ShutdownOnIOThread() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  prefetchers_.clear();

[dominich, 2012/07/23 16:04:41]

you're relying on linked_ptr to delete these? Is there a ScopedMap instead that
you can use?

[Shishir, 2012/08/01 22:35:24]

Nope, no ScopedMap in codebase. Using a ElementDeleter.

+}
+
+void ResourcePrefetcherManager::MaybeAddPrefetch(
+    const NavigationID& navigation_id,
+    scoped_ptr<ResourcePrefetcher::RequestVector> requests) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  const GURL& main_frame_url = navigation_id.main_frame_url;
+  if (prefetchers_.find(main_frame_url) != prefetchers_.end())
+    return;
+
+  ResourcePrefetcher* prefetcher = new ResourcePrefetcher(
+      this, config_, navigation_id, requests.Pass());
+  prefetchers_[main_frame_url] = make_linked_ptr(prefetcher);

[dominich, 2012/07/23 16:04:41]

double lookup.

[Shishir, 2012/08/01 22:35:24]

I can't combine them unless I create the prefetcher in advance and then delete
it later. Makes more sense to leave as is.

+  prefetcher->Start();
+}
+
+void ResourcePrefetcherManager::MaybeRemovePrefetch(
+    const NavigationID& navigation_id) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  const GURL& main_frame_url = navigation_id.main_frame_url;
+  if (prefetchers_.find(main_frame_url) != prefetchers_.end()) {
+    ResourcePrefetcher* prefetcher = prefetchers_[main_frame_url].get();

[dominich, 2012/07/23 16:04:41]

double lookup.

[Shishir, 2012/08/01 22:35:24]

Done.

+    if (prefetcher->navigation_id() == navigation_id)
+      prefetcher->Stop();
+  }
+}
+
+void ResourcePrefetcherManager::ResourcePrefetcherFinished(
+    ResourcePrefetcher* resource_prefetcher,
+    scoped_ptr<ResourcePrefetcher::RequestVector> requests) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  const GURL& main_frame_url =
+      resource_prefetcher->navigation_id().main_frame_url;
+  DCHECK(prefetchers_.find(main_frame_url) != prefetchers_.end());
+
+  // Our delegate can only be accessed from the UI thread.
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+      base::Bind(&ResourcePrefetcherManager::ResourcePrefetcherFinishedOnUI,
+                 this,
+                 resource_prefetcher->navigation_id(),
+                 base::Passed(requests.Pass())));
+
+  prefetchers_.erase(main_frame_url);

[dominich, 2012/07/23 16:04:41]

i think an explicit delete here is better than linked_ptr overhead.

[Shishir, 2012/08/01 22:35:24]

Done. Although I should point out we are looking at one linked_ptr per
navigation.

+}
+
+void ResourcePrefetcherManager::ResourcePrefetcherFinishedOnUI(
+    const NavigationID& navigation_id,
+    scoped_ptr<ResourcePrefetcher::RequestVector> requests) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  // Notify our delegate.
+  if (delegate_)

[dominich, 2012/07/23 16:04:41]

you CHECK(delegate_) in the ctor. this is unnecessary.

[Shishir, 2012/08/01 22:35:24]

Its required because the predictor_ is set to null in the ShutdownOnUIThread
call.

+    delegate_->FinishedPrefetchForNavigation(navigation_id,
+                                             requests.Pass());
+}
+
+net::URLRequestContext* ResourcePrefetcherManager::GetURLRequestContext() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  return context_getter_->GetURLRequestContext();
+}
+
+}  // namespace predictors