Add a signal to the scheduler that a navigation is expected

components/scheduler/renderer/renderer_scheduler.h

Index: components/scheduler/renderer/renderer_scheduler.h
diff --git a/components/scheduler/renderer/renderer_scheduler.h b/components/scheduler/renderer/renderer_scheduler.h
index 76755e84eee06b1de95318bfd8a37e35accf4388..7d4409fb61ea999db4571bc7d6a606e021e3218b 100644
--- a/components/scheduler/renderer/renderer_scheduler.h
+++ b/components/scheduler/renderer/renderer_scheduler.h
@@ -114,10 +114,19 @@ class SCHEDULER_EXPORT RendererScheduler : public ChildScheduler {
   // 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