WebUI TaskManager: Add "Activate page" feature.

chrome/browser/task_manager/task_manager.h

Index: chrome/browser/task_manager/task_manager.h
diff --git a/chrome/browser/task_manager/task_manager.h b/chrome/browser/task_manager/task_manager.h
index 0d8ba5171ec86cc7712e34d85e74749ccc4156c3..8c8e101938e5918e6bea8262b9c8f4d0ccb4de50 100644
--- a/chrome/browser/task_manager/task_manager.h
+++ b/chrome/browser/task_manager/task_manager.h
@@ -322,6 +322,9 @@ class TaskManagerModel : public base::RefCountedThreadSafe<TaskManagerModel> {
   // resource for the given row isn't a renderer.
   bool GetV8Memory(int index, size_t* result) const;
 
+  // Returns true if resource for the given row can be activated.
+  bool CanActivate(int index) const;
+
   // Returns true if resource for the given row can be inspected using developer
   // tools.
   bool CanInspect(int index) const;