Add ResumeRenderer to RendererScheduler for Purge+Suspend.

third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h

Index: third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h
diff --git a/third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h b/third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h
index 2a865e880158a249099df7e66d6f0d4474ae05f1..c6d3768f0cadd48c1dac05f30e90e2b2554a43ab 100644
--- a/third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h
+++ b/third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h
@@ -132,6 +132,11 @@ class BLINK_PLATFORM_EXPORT RendererScheduler : public ChildScheduler {
   // automatically resumed when foregrounded.
   virtual void SuspendRenderer() = 0;
 
+  // Tells the scheduler that the render process should be resumed. This can
+  // only be done when the renderer is suspended. The renderer will be
+  // automatically suspended again if continuously backgrounded.

[Sami, 2016/10/24 17:19:45]

This re-suspension logic is not a part of this patch, right? Also is it
something RendererScheduler is going to do automatically, or will we rely on
someone else calling SuspendRenderer again at an appropriate time?

If the RendererScheduler is going to control that automatically, then I think
ResumeRenderer should be called something like ResumeRendererTemporarily() to
make it clear that re-suspension will happen eventually.

[tasak, 2016/10/25 03:10:58]

Yeah, not a part of this patch.
I modified the comment, i.e. TabManager / MemoryCoordinator will suspend the
renderer.

+  virtual void ResumeRenderer() = 0;
+
   // Tells the scheduler that a navigation task is pending. While any main-frame
   // 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