PlzNavigate: implement process reuse for ServiceWorkers

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 4b8da41c0162081e2f28950e3fa15fba28df747e..0e30f25ad8c6dd539c5963fe4e5058ca2e368c28 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -629,6 +629,67 @@ class RenderProcessHostIsReadyObserver : public RenderProcessHostObserver {
   DISALLOW_COPY_AND_ASSIGN(RenderProcessHostIsReadyObserver);
 };
 
+// The following object is used to keep track of which sites
+// RenderProcessHosts are hosting frames and expecting navigations to.
+// There are two of them per BrowserContext, one for frames and one for
+// navigations.
+const void* const kCommittedSiteCountPerProcessTrackerKey =
+    "CommittedSiteCountPerProcessTrackerKey";
+const void* const kPendingSiteCountPerProcessTrackerKey =
+    "PendingSiteCountPerProcessTrackerKey";
+class SiteCountPerProcessTracker : public base::SupportsUserData::Data {
+ public:
+  SiteCountPerProcessTracker() {}
+  ~SiteCountPerProcessTracker() override {}
+
+  void AddCountForSiteForProcess(int render_process_host_id,
+                                 const GURL& site_url) {
+    std::map<ProcessID, Count>& counts_per_process = map_[site_url];
+    ++counts_per_process[render_process_host_id];
+  }
+
+  void RemoveCountForSiteForProcess(int render_process_host_id,
+                                    const GURL& site_url) {
+    auto result = map_.find(site_url);
+    DCHECK(result != map_.end());
+    std::map<ProcessID, Count>& counts_per_process = result->second;
+
+    --counts_per_process[render_process_host_id];
+    DCHECK(counts_per_process[render_process_host_id] >= 0);
+
+    if (counts_per_process[render_process_host_id] == 0)
+      counts_per_process.erase(render_process_host_id);
+
+    if (counts_per_process.empty())
+      map_.erase(site_url);
+  }
+
+  void FindRenderProcessesForSite(
+      const GURL& site_url,
+      std::set<RenderProcessHost*>* foreground_processes,
+      std::set<RenderProcessHost*>* background_processes) {
+    auto result = map_.find(site_url);
+    if (result == map_.end())
+      return;
+
+    std::map<ProcessID, Count>& counts_per_process = result->second;
+    for (auto iter : counts_per_process) {
+      RenderProcessHost* host = RenderProcessHost::FromID(iter.first);
+      DCHECK(host);
+      if (host->VisibleWidgetCount())
+        foreground_processes->insert(host);
+      else
+        background_processes->insert(host);
+    }
+  }
+
+ private:
+  using ProcessID = int;
+  using Count = int;
+  using CountPerProcessPerSiteMap = std::map<GURL, std::map<ProcessID, Count>>;
+  CountPerProcessPerSiteMap map_;
+};
+
 }  // namespace
 
 RendererMainThreadFactoryFunction g_renderer_main_thread_factory = NULL;
@@ -1748,6 +1809,82 @@ void RenderProcessHostImpl::set_render_process_host_factory(
   g_render_process_host_factory_ = rph_factory;
 }
 
+// static
+void RenderProcessHostImpl::AddFrameWithSite(
+    BrowserContext* browser_context,
+    RenderProcessHost* render_process_host,
+    const GURL& site_url) {
+  if (site_url.is_empty())
+    return;
+
+  SiteCountPerProcessTracker* tracker =
+      static_cast<SiteCountPerProcessTracker*>(browser_context->GetUserData(
+          kCommittedSiteCountPerProcessTrackerKey));
+  if (!tracker) {
+    tracker = new SiteCountPerProcessTracker();
+    browser_context->SetUserData(kCommittedSiteCountPerProcessTrackerKey,
+                                 base::WrapUnique(tracker));
+  }
+  tracker->AddCountForSiteForProcess(render_process_host->GetID(), site_url);
+}
+
+// static
+void RenderProcessHostImpl::RemoveFrameWithSite(
+    BrowserContext* browser_context,
+    RenderProcessHost* render_process_host,
+    const GURL& site_url) {
+  if (site_url.is_empty())
+    return;
+
+  SiteCountPerProcessTracker* tracker =
+      static_cast<SiteCountPerProcessTracker*>(browser_context->GetUserData(
+          kCommittedSiteCountPerProcessTrackerKey));
+  if (!tracker) {
+    tracker = new SiteCountPerProcessTracker();
+    browser_context->SetUserData(kCommittedSiteCountPerProcessTrackerKey,
+                                 base::WrapUnique(tracker));
+  }
+  tracker->RemoveCountForSiteForProcess(render_process_host->GetID(), site_url);
+}
+
+// static
+void RenderProcessHostImpl::AddExpectedNavigationToSite(
+    BrowserContext* browser_context,
+    RenderProcessHost* render_process_host,
+    const GURL& site_url) {
+  if (site_url.is_empty())
+    return;
+
+  SiteCountPerProcessTracker* tracker =
+      static_cast<SiteCountPerProcessTracker*>(
+          browser_context->GetUserData(kPendingSiteCountPerProcessTrackerKey));
+  if (!tracker) {
+    tracker = new SiteCountPerProcessTracker();
+    browser_context->SetUserData(kPendingSiteCountPerProcessTrackerKey,
+                                 base::WrapUnique(tracker));
+  }
+  tracker->AddCountForSiteForProcess(render_process_host->GetID(), site_url);
+}
+
+// static
+void RenderProcessHostImpl::RemoveExpectedNavigationToSite(
+    BrowserContext* browser_context,
+    RenderProcessHost* render_process_host,
+    const GURL& site_url) {
+  if (site_url.is_empty())
+    return;
+
+  SiteCountPerProcessTracker* tracker =
+      static_cast<SiteCountPerProcessTracker*>(
+          browser_context->GetUserData(kPendingSiteCountPerProcessTrackerKey));
+  if (!tracker) {
+    tracker = new SiteCountPerProcessTracker();
+    browser_context->SetUserData(kPendingSiteCountPerProcessTrackerKey,
+                                 base::WrapUnique(tracker));
+  }
+  tracker->RemoveCountForSiteForProcess(render_process_host->GetID(), site_url);
+}
+
 bool RenderProcessHostImpl::IsForGuestsOnly() const {
   return is_for_guests_only_;
 }
@@ -2864,6 +3001,9 @@ RenderProcessHost* RenderProcessHostImpl::GetProcessHostForSiteInstance(
       DCHECK(SiteIsolationPolicy::IsTopDocumentIsolationEnabled());
       render_process_host = GetDefaultSubframeProcessHost(
           browser_context, site_instance, is_for_guests_only);
+    case SiteInstanceImpl::ProcessReusePolicy::REUSE_PENDING_OR_COMMITTED_SITE:
+      render_process_host =
+          FindReusableProcessHostForSite(browser_context, site_url);
       break;
     default:
       break;
@@ -3257,6 +3397,55 @@ RenderProcessHost* RenderProcessHostImpl::GetDefaultSubframeProcessHost(
   return holder->GetProcessHost(site_instance, is_for_guests_only);
 }
 
+// static
+RenderProcessHost* RenderProcessHostImpl::FindReusableProcessHostForSite(
+    BrowserContext* browser_context,
+    const GURL& site_url) {
+  if (site_url.is_empty())
+    return nullptr;
+
+  std::set<RenderProcessHost*> eligible_foreground_hosts;
+  std::set<RenderProcessHost*> eligible_background_hosts;
+
+  // Add the RenderProcessHosts hosting a frame for |site_url| to the list of
+  // eligible RenderProcessHosts.
+  SiteCountPerProcessTracker* committed_tracker =
+      static_cast<SiteCountPerProcessTracker*>(browser_context->GetUserData(
+          kCommittedSiteCountPerProcessTrackerKey));
+  if (committed_tracker) {
+    committed_tracker->FindRenderProcessesForSite(
+        site_url, &eligible_foreground_hosts, &eligible_background_hosts);
+  }
+
+  // Add the RenderProcessHosts expecting a navigation to |site_url| to the list
+  // of eligible RenderProcessHosts.
+  SiteCountPerProcessTracker* pending_tracker =
+      static_cast<SiteCountPerProcessTracker*>(
+          browser_context->GetUserData(kPendingSiteCountPerProcessTrackerKey));
+  if (pending_tracker) {
+    pending_tracker->FindRenderProcessesForSite(
+        site_url, &eligible_foreground_hosts, &eligible_background_hosts);
+  }
+
+  if (!eligible_foreground_hosts.empty()) {
+    int index = base::RandInt(0, eligible_foreground_hosts.size() - 1);
+    auto iterator = eligible_foreground_hosts.begin();
+    for (int i = 0; i < index; ++i)
+      ++iterator;
+    return (*iterator);
+  }
+
+  if (!eligible_background_hosts.empty()) {
+    int index = base::RandInt(0, eligible_background_hosts.size() - 1);
+    auto iterator = eligible_background_hosts.begin();
+    for (int i = 0; i < index; ++i)
+      ++iterator;
+    return (*iterator);
+  }
+
+  return nullptr;
+}
+
 #if BUILDFLAG(ENABLE_WEBRTC)
 void RenderProcessHostImpl::OnRegisterAecDumpConsumer(int id) {
   BrowserThread::PostTask(