Add a default implementation in metrics_default.cc of histograms methods in system_wrappers/interfac

webrtc/test/BUILD.gn

Index: webrtc/test/BUILD.gn
diff --git a/webrtc/test/BUILD.gn b/webrtc/test/BUILD.gn
index af9516f43426c54a3eada81e3fcfc7c7e57dd8f5..5951693a500eedcd70f721e9fabe40635a4bd189 100644
--- a/webrtc/test/BUILD.gn
+++ b/webrtc/test/BUILD.gn
@@ -34,21 +34,6 @@ source_set("field_trial") {
   public_configs = [ "..:common_inherited_config" ]
 }
 
-source_set("histogram") {
-  sources = [
-    "histogram.cc",
-    "histogram.h",
-  ]
-
-  deps = [
-    "..:webrtc_common",
-    "../system_wrappers",
-  ]
-
-  configs += [ "..:common_config" ]
-  public_configs = [ "..:common_inherited_config" ]
-}
-
 source_set("test_support") {
   testonly = true
 
@@ -100,8 +85,8 @@ source_set("test_support_main") {
 
   deps = [
     ":field_trial",
-    ":histogram",
     ":test_support",
+    "../system_wrappers:metrics_default",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/gflags",