Allows prefetch requests to live beyond the renderer by delaying

content/browser/loader/resource_loader.cc

Index: content/browser/loader/resource_loader.cc
diff --git a/content/browser/loader/resource_loader.cc b/content/browser/loader/resource_loader.cc
index 88c9c857d55e21cb6b8017de3f08821b32cf8964..c17f6e228f2f02dc1154b7b0552788ea08995197 100644
--- a/content/browser/loader/resource_loader.cc
+++ b/content/browser/loader/resource_loader.cc
@@ -7,7 +7,9 @@
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/time/time.h"
+#include "base/timer/timer.h"
 #include "content/browser/child_process_security_policy_impl.h"
 #include "content/browser/loader/cross_site_resource_handler.h"
 #include "content/browser/loader/resource_loader_delegate.h"
@@ -64,6 +66,10 @@ void PopulateResourceResponse(net::URLRequest* request,
 
 }  // namespace
 
+// The time in ms to delay a cancel of a detachable resource unless otherwise
+// specified by a flag.
+static const int kDefaultDelayDetachableCancelMs = 60000;
+
 ResourceLoader::ResourceLoader(scoped_ptr<net::URLRequest> request,
                                scoped_ptr<ResourceHandler> handler,
                                ResourceLoaderDelegate* delegate)
@@ -458,6 +464,33 @@ void ResourceLoader::StartRequestInternal() {
   delegate_->DidStartRequest(this);
 }
 
+bool ResourceLoader::DelayCancelForDetachable(
+    const ResourceRequestInfoImpl& info, bool from_renderer) {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  // Delay requests to cancel detachable resources. Detachable resources are
+  // those that may need to live beyond the lifetime of their renderers, but
+  // should not be allowed to continue indefinitely as the user cannot control
+  // them through the UI. Examples of detachable resources include prefetches
+  // and <a ping>.
+  if (from_renderer && !detached_timer_ && info.is_detachable() &&
+      command_line.HasSwitch(switches::kDelayDetachableCancellation)) {

[asanka, 2013/10/14 21:06:49]

Is it possible to get two cancels from the renderer? So far that would have been
"idempotent". But it seems this code would delay one but not the other.

+    // Start the delay timer.
+    detached_timer_.reset(new base::OneShotTimer<ResourceLoader>());
+
+    int delay_ms;
+    if (!base::StringToInt(command_line.GetSwitchValueASCII(
+                               switches::kDelayDetachableCancellation),
+                           &delay_ms)) {
+      delay_ms = kDefaultDelayDetachableCancelMs;
+    }
+
+    detached_timer_->Start(FROM_HERE, TimeDelta::FromMilliseconds(delay_ms),
+                           this, &ResourceLoader::Cancel);
+    return true;
+  }
+  return false;
+}
+
 void ResourceLoader::CancelRequestInternal(int error, bool from_renderer) {
   VLOG(1) << "CancelRequestInternal: " << request_->url().spec();
 
@@ -469,6 +502,10 @@ void ResourceLoader::CancelRequestInternal(int error, bool from_renderer) {
   if (from_renderer && (info->is_download() || info->is_stream()))
     return;
 
+  if (DelayCancelForDetachable(*info, from_renderer)) {
+    return;
+  }
+
   // TODO(darin): Perhaps we should really be looking to see if the status is
   // IO_PENDING?
   bool was_pending = request_->is_pending();