memory coordinator: Purge memory under memory pressure

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 1a0f300f2522f28800561d1cde40248b0bb6e14f..83530b1e130bfed8c545023ea2fb645901fa2779 100644
--- a/content/public/browser/memory_coordinator_delegate.h
+++ b/content/public/browser/memory_coordinator_delegate.h
@@ -19,8 +19,8 @@ class CONTENT_EXPORT MemoryCoordinatorDelegate {
 
   // 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() {}
+  // effect and returns false.
+  virtual bool DiscardTab();
 };
 
 }  // namespace content