Change VirtualTimePolicy::PAUSE_IF_NETWORK_FETCHES_PENDING

components/scheduler/renderer/web_view_scheduler_impl.cc

 // Copyright 2015 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 "components/scheduler/renderer/web_view_scheduler_impl.h"
 
 #include "base/logging.h"
+#include "components/scheduler/base/real_time_domain.h"
 #include "components/scheduler/base/virtual_time_domain.h"
 #include "components/scheduler/child/scheduler_tqm_delegate.h"
 #include "components/scheduler/renderer/auto_advancing_virtual_time_domain.h"
 #include "components/scheduler/renderer/renderer_scheduler_impl.h"
 #include "components/scheduler/renderer/web_frame_scheduler_impl.h"
 #include "third_party/WebKit/public/platform/WebFrameScheduler.h"
 #include "third_party/WebKit/public/web/WebConsoleMessage.h"
 #include "third_party/WebKit/public/web/WebFrame.h"
 #include "third_party/WebKit/public/web/WebView.h"
 
 namespace scheduler {
 
 WebViewSchedulerImpl::WebViewSchedulerImpl(
     blink::WebView* web_view,
     RendererSchedulerImpl* renderer_scheduler,
     bool disable_background_timer_throttling)
     : virtual_time_pump_policy_(TaskQueue::PumpPolicy::AUTO),
       web_view_(web_view),
       renderer_scheduler_(renderer_scheduler),
       virtual_time_policy_(VirtualTimePolicy::ADVANCE),
       page_visible_(true),
       disable_background_timer_throttling_(disable_background_timer_throttling),
-      allow_virtual_time_to_advance_(true) {
+      allow_virtual_time_to_advance_(true),
+      have_seen_loading_task_(false) {
   renderer_scheduler->AddWebViewScheduler(this);
 }
 
 WebViewSchedulerImpl::~WebViewSchedulerImpl() {
   // TODO(alexclarke): Find out why we can't rely on the web view outliving the
   // frame.
   for (WebFrameSchedulerImpl* frame_scheduler : frame_schedulers_) {
     frame_scheduler->DetachFromWebViewScheduler();
   }
   renderer_scheduler_->RemoveWebViewScheduler(this);
-  if (virtual_time_domain_)
+  if (virtual_time_domain_) {
+    // Since we're just about to delete virtual_time_domain_ we'd better move
+    // the per-thread task queues back to the RealTimeDomain or we risk a UAF
+    // when the task queues get deleted.
+    renderer_scheduler_->SetPerThreadTaskRunnerTimeDomain(
+        renderer_scheduler_->real_time_domain());
     renderer_scheduler_->UnregisterTimeDomain(virtual_time_domain_.get());
+  }
 }
 
 void WebViewSchedulerImpl::setPageVisible(bool page_visible) {
   if (disable_background_timer_throttling_ || page_visible_ == page_visible)
     return;
 
   page_visible_ = page_visible;
 
   for (WebFrameSchedulerImpl* frame_scheduler : frame_schedulers_) {
     frame_scheduler->setPageVisible(page_visible_);
@@ skipping 38 matching lines @@
   virtual_time_domain_.reset(new AutoAdvancingVirtualTimeDomain(
       renderer_scheduler_->tick_clock()->NowTicks()));
   renderer_scheduler_->RegisterTimeDomain(virtual_time_domain_.get());
 
   virtual_time_domain_->SetCanAdvanceVirtualTime(
       allow_virtual_time_to_advance_);
 
   for (WebFrameSchedulerImpl* frame_scheduler : frame_schedulers_) {
     frame_scheduler->OnVirtualTimeDomainChanged();
   }
+
+  // For determinism the per-thread task queues must use virtual time too.
+  renderer_scheduler_->SetPerThreadTaskRunnerTimeDomain(
+        virtual_time_domain_.get());
 }
 
 void WebViewSchedulerImpl::setAllowVirtualTimeToAdvance(
     bool allow_virtual_time_to_advance) {
   if (allow_virtual_time_to_advance_ == allow_virtual_time_to_advance)
     return;
 
   allow_virtual_time_to_advance_ = allow_virtual_time_to_advance;
 
   if (virtual_time_domain_) {
     virtual_time_domain_->SetCanAdvanceVirtualTime(
         allow_virtual_time_to_advance);
   }
 }
 
 bool WebViewSchedulerImpl::virtualTimeAllowedToAdvance() const {
   return allow_virtual_time_to_advance_;
 }
 
 void WebViewSchedulerImpl::DidStartLoading(unsigned long identifier) {
   pending_loads_.insert(identifier);
+  have_seen_loading_task_ = true;
 
   if (virtual_time_policy_ !=
       VirtualTimePolicy::PAUSE_IF_NETWORK_FETCHES_PENDING) {
     return;
   }
 
   if (pending_loads_.size() == 1u)
     setAllowVirtualTimeToAdvance(false);
 }
 
@@ skipping 15 matching lines @@
   switch (virtual_time_policy_) {
     case VirtualTimePolicy::ADVANCE:
       setAllowVirtualTimeToAdvance(true);
       break;
 
     case VirtualTimePolicy::PAUSE:
       setAllowVirtualTimeToAdvance(false);
       break;
 
     case VirtualTimePolicy::PAUSE_IF_NETWORK_FETCHES_PENDING:
-      setAllowVirtualTimeToAdvance(pending_loads_.size() == 0);
+      // We pause virtual time until we've seen a loading task posted, because
+      // otherwise we could advance virtual time arbitarially far before the
+      // first load arrives.
+      setAllowVirtualTimeToAdvance(pending_loads_.size() == 0 &&
+                                   have_seen_loading_task_);
       break;
   }
 }
 
 }  // namespace scheduler