Improve performance of proxy resolver by tracing DNS dependencies.

net/base/mock_host_resolver.h

Index: net/base/mock_host_resolver.h
diff --git a/net/base/mock_host_resolver.h b/net/base/mock_host_resolver.h
index 5542a64cf9da942cce34bfb39936a5f7edd40985..fad529de4a178cd91954f162e7e91583345ff75c 100644
--- a/net/base/mock_host_resolver.h
+++ b/net/base/mock_host_resolver.h
@@ -94,6 +94,16 @@ class MockHostResolverBase : public HostResolver,
   // ResolveAllPending().
   bool has_pending_requests() const { return !requests_.empty(); }
 
+  // The number of times that Resolve() has been called.
+  size_t num_resolve() const {
+    return num_resolve_;
+  }
+
+  // The number of times that ResolveFromCache() has been called.
+  size_t num_resolve_from_cache() const {
+    return num_resolve_from_cache_;
+  }
+
  protected:
   explicit MockHostResolverBase(bool use_caching);
 
@@ -117,6 +127,9 @@ class MockHostResolverBase : public HostResolver,
   RequestMap requests_;
   size_t next_request_id_;
 
+  size_t num_resolve_;
+  size_t num_resolve_from_cache_;
+
   DISALLOW_COPY_AND_ASSIGN(MockHostResolverBase);
 };
 
@@ -175,6 +188,9 @@ class RuleBasedHostResolverProc : public HostResolverProc {
   // Simulate a lookup failure for |host| (it also can be a pattern).
   void AddSimulatedFailure(const std::string& host);
 
+  // Deletes all the rules that have been added.
+  void ClearRules();
+
   // HostResolverProc methods:
   virtual int Resolve(const std::string& host,
                       AddressFamily address_family,