Add a signal to the scheduler that a navigation is expected

components/scheduler/renderer/renderer_scheduler.h

 // Copyright 2014 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.
 
 #ifndef COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 #define COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 
 #include "base/message_loop/message_loop.h"
 #include "components/scheduler/child/child_scheduler.h"
 #include "components/scheduler/child/single_thread_idle_task_runner.h"
@@ skipping 96 matching lines @@
   // driven by this process. A stricter condition than |OnRendererHidden()|, the
   // process is assumed to be foregrounded when the scheduler is constructed.
   // Must be called on the main thread.
   virtual void OnRendererBackgrounded() = 0;
 
   // Tells the scheduler that the renderer process has been foregrounded.
   // This is the assumed state when the scheduler is constructed.
   // Must be called on the main thread.
   virtual void OnRendererForegrounded() = 0;
 
-  // Tells the scheduler that a page load has started.  The scheduler will
+  // Tells the scheduler that a navigation task is pending. While any navigation
+  // tasks are pending, the scheduler will ensure that loading tasks are not
+  // blocked even if they are expensive. Must be called on the main thread.
+  virtual void NavigationTaskPendingIncRef() = 0;

[Sami, 2015/09/25 16:18:38]

nit: I think the "reference" part here is a little misleading since nothing is
really being referenced. How about just
AddPendingNavigation/RemovePendingNavigation?

[alex clarke (OOO till 29th), 2015/09/25 16:57:38]

Done.

+
+  // Tells the scheduler that a navigation task is no longer pending.
+  // Must be called on the main thread.
+  virtual void NavigationTaskPendingDecRef() = 0;
+
+  // Tells the scheduler that a navigation has started.  The scheduler will
   // prioritize loading tasks for a short duration afterwards.
   // Must be called from the main thread.
-  virtual void OnPageLoadStarted() = 0;
+  virtual void OnNavigationStarted() = 0;
 
   // Returns true if the scheduler has reason to believe that high priority work
   // may soon arrive on the main thread, e.g., if gesture events were observed
   // recently.
   // Must be called from the main thread.
   virtual bool IsHighPriorityWorkAnticipated() = 0;
 
   // Suspends the timer queue and increments the timer queue suspension count.
   // May only be called from the main thread.
   virtual void SuspendTimerQueue() = 0;
 
   // Decrements the timer queue suspension count and re-enables the timer queue
   // if the suspension count is zero and the current schduler policy allows it.
   virtual void ResumeTimerQueue() = 0;
 
   // Sets whether to allow suspension of timers after the backgrounded signal is
   // received via OnRendererBackgrounded. Defaults to disabled.
   virtual void SetTimerQueueSuspensionWhenBackgroundedEnabled(bool enabled) = 0;
 
  protected:
   RendererScheduler();
   DISALLOW_COPY_AND_ASSIGN(RendererScheduler);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_