Create webrtc/base/objc and move some logging code there

webrtc/base/BUILD.gn

Index: webrtc/base/BUILD.gn
diff --git a/webrtc/base/BUILD.gn b/webrtc/base/BUILD.gn
index 6d51003fed02a5911ee21511d9d7b8012688a884..4f42695854594320ec611d610d385df9ed867fb0 100644
--- a/webrtc/base/BUILD.gn
+++ b/webrtc/base/BUILD.gn
@@ -605,3 +605,19 @@ static_library("rtc_base") {
     defines += [ "timezone=_timezone" ]
   }
 }
+
+if (is_ios) {
+  source_set("rtc_base_objc") {
+    deps = [
+      ":rtc_base",
+    ]
+    cflags = [ "-fobjc-arc" ]
+    configs += [ "..:common_config" ]
+    public_configs = [ "..:common_inherited_config" ]
+
+    sources = [
+      "objc/RTCLogging.h",
+      "objc/RTCLogging.mm",
+    ]
+  }
+}