Add LoadState reporting to the mojo proxy resolver.

net/proxy/proxy_resolver_v8_tracing.h

Index: net/proxy/proxy_resolver_v8_tracing.h
diff --git a/net/proxy/proxy_resolver_v8_tracing.h b/net/proxy/proxy_resolver_v8_tracing.h
index 85aca519e7e2aa68df30ccc06f9613a4a61cc677..8840b6559de1134f1b99c52f204c89694485782b 100644
--- a/net/proxy/proxy_resolver_v8_tracing.h
+++ b/net/proxy/proxy_resolver_v8_tracing.h
@@ -42,6 +42,20 @@ class NET_EXPORT_PRIVATE ProxyResolverV8Tracing
                          ProxyResolverErrorObserver* error_observer,
                          NetLog* net_log);
 
+  // Constructs a ProxyResolver that will issue DNS requests through
+  // |host_resolver|, forward Javascript errors through |error_observer|, and
+  // log Javascript errors and alerts to |net_log|. When the LoadState for a
+  // request changes, |on_load_state_changed| will be invoked with the
+  // RequestHandle for that request with the new LoadState.
+  //
+  // Note that the constructor takes ownership of |error_observer|, whereas
+  // |host_resolver| and |net_log| are expected to outlive |this|.
+  ProxyResolverV8Tracing(
+      HostResolver* host_resolver,
+      ProxyResolverErrorObserver* error_observer,
+      NetLog* net_log,
+      const LoadStateChangedCallback<RequestHandle>& on_load_state_changed);
+
   ~ProxyResolverV8Tracing() override;
 
   // ProxyResolver implementation:
@@ -75,6 +89,9 @@ class NET_EXPORT_PRIVATE ProxyResolverV8Tracing
   // The number of outstanding (non-cancelled) jobs.
   int num_outstanding_callbacks_;
 
+  // Invoked when the load state for a request changes.
+  const LoadStateChangedCallback<RequestHandle> on_load_state_changed_;
+
   DISALLOW_COPY_AND_ASSIGN(ProxyResolverV8Tracing);
 };