Implement LoadLog, and hook up HostResolverImpl to LoadLog....

net/base/load_log.h

Index: net/base/load_log.h
===================================================================
--- net/base/load_log.h	(revision 23403)
+++ net/base/load_log.h	(working copy)
@@ -5,7 +5,10 @@
 #ifndef NET_BASE_LOAD_LOG_H_
 #define NET_BASE_LOAD_LOG_H_
 
+#include <vector>
+
 #include "base/ref_counted.h"
+#include "base/time.h"
 
 namespace net {
 
@@ -13,10 +16,87 @@
 // a request (waiting in queues, resolving hosts, resolving proxy, etc...).
 class LoadLog : public base::RefCounted<LoadLog> {
  public:
-// TODO(eroman): Add an API similar to:
-//     void TrackEnterState(LoadState state);
-//     void TrackLeaveState(LoadState state);
-//     void Merge(const LoadLog* other);
+
+  enum EventType {
+#define EVENT_TYPE(label) TYPE_ ## label,
+#include "net/base/load_log_event_type_list.h"
+#undef EVENT_TYPE
+  };
+
+  // Whether this is the start/end of an event. Or in the case of EventTypes
+  // that are "instantaneous", kNone.
+  enum EventPhase {
+    PHASE_NONE,
+    PHASE_BEGIN,
+    PHASE_END,
+  };
+
+  // A logged event. Note that "phase" means if this is the start/end of a
+  // particular event type (in order to record a timestamp for both endpoints).
+  struct Event {
+    Event(base::TimeTicks time,
+          EventType type,
+          EventPhase phase)
+        : time(time), type(type), phase(phase) {
+    }
+
+    base::TimeTicks time;
+    EventType type;
+    EventPhase phase;
+  };
+
+  // The maximum size of |events_|.
+  enum { kMaxNumEntries = 25 };
+
+  // Ordered set of events that were logged.
+  // TODO(eroman): use a StackVector or array to avoid allocations.
+  typedef std::vector<Event> EventList;
+
+  // Create a log, which can hold up to |kMaxNumEntries| Events.
+  //
+  // If events are dropped because the log has grown too large, the final
+  // entry will be of type kLogTruncated.
+  LoadLog();
+
+  // --------------------------------------------------------------------------
+
+  // The public interface for adding events to the log are static methods.
+  // This makes it easier to deal with optionally NULL LoadLog.
+
+  // Adds an instantaneous event to the log.
+  static void AddEvent(LoadLog* log, EventType event) {
+    if (log)
+      log->Add(base::TimeTicks::Now(), event, PHASE_NONE);
+  }
+
+  // Adds the start of an event to the log. Presumably this event type measures
+  // a time duration, and will be matched by a call to EndEvent(event).
+  static void BeginEvent(LoadLog* log, EventType event) {
+    if (log)
+      log->Add(base::TimeTicks::Now(), event, PHASE_BEGIN);
+  }
+
+  // Adds the end of an event to the log. Presumably this event type measures
+  // a time duration, and we are matching an earlier call to BeginEvent(event).
+  static void EndEvent(LoadLog* log, EventType event) {
+    if (log)
+      log->Add(base::TimeTicks::Now(), event, PHASE_END);
+  }
+
+  // --------------------------------------------------------------------------
+
+  // Returns the list of all events in the log.
+  const EventList& events() const {
+    return events_;
+  }
+
+  // Returns a C-String symbolic name for |event|.
+  static const char* EventTypeToString(EventType event);
+
+  void Add(base::TimeTicks t, EventType event, EventPhase phase);
+
+ private:
+  EventList events_;
 };
 
 }  // namespace net