Split ProxyResolverV8Tracing into an implementation and a wrapper.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 63ad03cc03b81abc1a29f9570cb1b8abb88778bb..b458773750067fea4444fe30d182b422a7e1a5ad 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -764,6 +764,8 @@ if (use_v8_in_net) {
       "proxy/proxy_resolver_v8.h",
       "proxy/proxy_resolver_v8_tracing.cc",
       "proxy/proxy_resolver_v8_tracing.h",
+      "proxy/proxy_resolver_v8_tracing_wrapper.cc",
+      "proxy/proxy_resolver_v8_tracing_wrapper.h",
       "proxy/proxy_service_v8.cc",
       "proxy/proxy_service_v8.h",
     ]
@@ -835,8 +837,6 @@ if (use_v8_in_net && !is_android) {
     sources = [
       "dns/host_resolver_mojo.cc",
       "dns/host_resolver_mojo.h",
-      "proxy/load_state_change_coalescer.cc",
-      "proxy/load_state_change_coalescer.h",
       "proxy/mojo_proxy_resolver_factory_impl.cc",
       "proxy/mojo_proxy_resolver_factory_impl.h",
       "proxy/mojo_proxy_resolver_impl.cc",
@@ -1494,7 +1494,6 @@ if (!is_android && !is_mac) {
       sources -= [
         "dns/host_resolver_mojo_unittest.cc",
         "dns/mojo_host_resolver_impl_unittest.cc",
-        "proxy/load_state_change_coalescer_unittest.cc",
         "proxy/mojo_proxy_resolver_factory_impl_unittest.cc",
         "proxy/mojo_proxy_resolver_impl_unittest.cc",
         "proxy/proxy_resolver_error_observer_mojo_unittest.cc",