content::ResourceDispatcherHostImpl changes for stale-while-revalidate

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index 6cc7f6196f95a3832224a5332cb20df0b113cf6c..4984c6e81c78a0f17912e31a92f10757bb9d14a2 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -19,6 +19,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/shared_memory.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/profiler/scoped_tracker.h"
@@ -473,10 +474,19 @@ ResourceDispatcherHostImpl::ResourceDispatcherHostImpl()
 
   update_load_states_timer_.reset(
       new base::RepeatingTimer<ResourceDispatcherHostImpl>());
+
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (base::FieldTrialList::FindFullName("StaleWhileRevalidate") == "Enabled" ||
+      command_line->HasSwitch(switches::kEnableStaleWhileRevalidate)) {
+    async_revalidation_manager_.reset(new AsyncRevalidationManager);
+  }
 }
 
 ResourceDispatcherHostImpl::~ResourceDispatcherHostImpl() {
   DCHECK(outstanding_requests_stats_map_.empty());
+  // It's not safe to destroy this object while AsyncRevalidationDriver objects
+  // have callbacks referencing it.
+  async_revalidation_manager_.reset();
   DCHECK(g_resource_dispatcher_host);
   g_resource_dispatcher_host = NULL;
 }
@@ -578,6 +588,13 @@ void ResourceDispatcherHostImpl::CancelRequestsForContext(
 
   loaders_to_cancel.clear();
 
+  if (async_revalidation_manager_) {
+    // Cancelling async revalidations should not result in the creation of new
+    // requests, but do it before the checks just to be on the safe side.
+    async_revalidation_manager_->CancelAsyncRevalidationsForResourceContext(
+        context);
+  }
+
   // Validate that no more requests for this context were added.
   for (LoaderMap::const_iterator i = pending_loaders_.begin();
        i != pending_loaders_.end(); ++i) {
@@ -824,6 +841,14 @@ void ResourceDispatcherHostImpl::DidReceiveRedirect(ResourceLoader* loader,
   if (!info->GetAssociatedRenderFrame(&render_process_id, &render_frame_host))
     return;
 
+  // Remove the LOAD_SUPPORT_ASYNC_REVALIDATION flag if it is present.

[Bence, 2015/11/17 13:12:23]

Please explain briefly why you do this for redirects.

[Adam Rice, 2015/11/17 17:45:53]

Done.

+  net::URLRequest* request = loader->request();
+  if (request->load_flags() & net::LOAD_SUPPORT_ASYNC_REVALIDATION) {
+    int new_load_flags = request->load_flags() &
+        ~net::LOAD_SUPPORT_ASYNC_REVALIDATION;
+    request->SetLoadFlags(new_load_flags);
+  }
+
   // Notify the observers on the UI thread.
   scoped_ptr<ResourceRedirectDetails> detail(new ResourceRedirectDetails(
       loader->request(),
@@ -846,6 +871,12 @@ void ResourceDispatcherHostImpl::DidReceiveResponse(ResourceLoader* loader) {
         info->GetChildID(), info->GetRouteID());
   }
 
+  if (request->response_info().async_revalidation_required && !is_shutdown_) {
+    DCHECK(async_revalidation_manager_);
+    async_revalidation_manager_->BeginAsyncRevalidation(request,
+                                                        scheduler_.get());
+  }
+
   int render_process_id, render_frame_host;
   if (!info->GetAssociatedRenderFrame(&render_process_id, &render_frame_host))
     return;
@@ -1279,6 +1310,14 @@ void ResourceDispatcherHostImpl::BeginRequest(
     load_flags |= net::LOAD_DO_NOT_USE_EMBEDDED_IDENTITY;
   }
 
+  // Check if request is eligible for async revalidation.

[Bence, 2015/11/17 13:12:23]

Optional: this comment seems to be redundant with the nicely chosen local
variable name, consider removing it.

[Adam Rice, 2015/11/17 17:45:53]

Done.

+  bool support_async_revalidation =
+      (!is_sync_load && async_revalidation_manager_ &&
+       AsyncRevalidationManager::QualifiesForAsyncRevalidation(request_data));
+
+  if (support_async_revalidation)
+    load_flags |= net::LOAD_SUPPORT_ASYNC_REVALIDATION;
+
   // Sync loads should have maximum priority and should be the only
   // requets that have the ignore limits flag set.
   if (is_sync_load) {
@@ -1312,7 +1351,8 @@ void ResourceDispatcherHostImpl::BeginRequest(
       request_data.referrer_policy,
       request_data.visiblity_state,
       resource_context, filter_->GetWeakPtr(),
-      !is_sync_load);
+      !is_sync_load,
+      support_async_revalidation ? request_data.headers : std::string());
   // Request takes ownership.
   extra_info->AssociateWithRequest(new_request.get());
 
@@ -1583,7 +1623,8 @@ ResourceRequestInfoImpl* ResourceDispatcherHostImpl::CreateRequestInfo(
       blink::WebPageVisibilityStateVisible,
       context,
       base::WeakPtr<ResourceMessageFilter>(),  // filter
-      true);                                   // is_async
+      true,                                    // is_async
+      std::string());                          // original_headers
 }
 
 void ResourceDispatcherHostImpl::OnRenderViewHostCreated(int child_id,
@@ -2026,7 +2067,8 @@ void ResourceDispatcherHostImpl::BeginNavigationRequest(
       blink::WebPageVisibilityStateVisible,
       resource_context,
       base::WeakPtr<ResourceMessageFilter>(),  // filter
-      true);
+      true,                                    // is_async
+      std::string());                          // original_headers
   // Request takes ownership.
   extra_info->AssociateWithRequest(new_request.get());
 
@@ -2060,6 +2102,12 @@ void ResourceDispatcherHostImpl::BeginNavigationRequest(
   BeginRequestInternal(new_request.Pass(), handler.Pass());
 }
 
+void ResourceDispatcherHostImpl::EnableStaleWhileRevalidateForTesting() {
+  // Do nothing if it is enabled already.
+  if (!async_revalidation_manager_)
+    async_revalidation_manager_.reset(new AsyncRevalidationManager);
+}
+
 // static
 int ResourceDispatcherHostImpl::CalculateApproximateMemoryCost(
     net::URLRequest* request) {