Improve performance of proxy resolver by tracing DNS dependencies.

net/base/capturing_net_log.h

Index: net/base/capturing_net_log.h
diff --git a/net/base/capturing_net_log.h b/net/base/capturing_net_log.h
index 413be5275a0bed0a1e67c30ab60000634f1346a7..ec78a3f643f0e781961bd0d371fb8303b9e00b52 100644
--- a/net/base/capturing_net_log.h
+++ b/net/base/capturing_net_log.h
@@ -54,6 +54,10 @@ class CapturingNetLog : public NetLog {
     // log entry.
     bool GetNetErrorCode(int* value) const;
 
+    // Returns the parameters as a JSON string, or empty string if there are no
+    // parameters.
+    std::string GetParamsJson() const;
+
     EventType type;
     base::TimeTicks time;
     Source source;