Expose DiscardTab() to MemoryCoordiantor

content/public/browser/memory_coordinator_delegate.h

Index: content/public/browser/memory_coordinator_delegate.h
diff --git a/content/public/browser/memory_coordinator_delegate.h b/content/public/browser/memory_coordinator_delegate.h
index 32758d964fa907e03dd97b30652e92385e700fa8..1a0f300f2522f28800561d1cde40248b0bb6e14f 100644
--- a/content/public/browser/memory_coordinator_delegate.h
+++ b/content/public/browser/memory_coordinator_delegate.h
@@ -16,6 +16,11 @@ class CONTENT_EXPORT MemoryCoordinatorDelegate {
 
   // Returns true when a given backgrounded renderer process can be suspended.
   virtual bool CanSuspendBackgroundedRenderer(int render_process_id) = 0;
+
+  // Requests to discard one tab. An implementation should select a low priority
+  // tab to discard. If there is no tab that can be discarded, this doesn't take
+  // effect.
+  virtual void DiscardTab() {}
 };
 
 }  // namespace content