memory_coordinator: Discard tabs under critical memory condition

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..d934fa3754a46d81637d74c95f800d717f36dfa4 100644
--- a/content/public/browser/memory_coordinator_delegate.h
+++ b/content/public/browser/memory_coordinator_delegate.h
@@ -12,15 +12,15 @@ namespace content {
 // A delegate class which is used by the memory coordinator.
 class CONTENT_EXPORT MemoryCoordinatorDelegate {
  public:
-  virtual ~MemoryCoordinatorDelegate() {}
+  virtual ~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() {}
+  // effect and returns false. Otherwise returns true.
+  virtual bool DiscardTab();
 };
 
 }  // namespace content