Consolidate constructormagic macros with Chromium version and remove Chromium override.

Part of work removing dependency on Chromium's base.

Only adds "= delete". From https://codereview.chromium.org/1151443003 :
"This will guarantee the error to be at compile time, and not rely on the call visibility (private)."

In consequence of that change, fixed an illegal copy and removed a bunch of unused variables.

Depends on https://codereview.webrtc.org/1345433002/

BUG=chromium:468375
(in particular comment #37)
NOTRY=true

Review URL: https://codereview.webrtc.org/1342543004

Cr-Commit-Position: refs/heads/master@{#9954}
diff --git a/webrtc/base/logging.cc b/webrtc/base/logging.cc
index affbb03..7e308c2 100644
--- a/webrtc/base/logging.cc
+++ b/webrtc/base/logging.cc
@@ -206,8 +206,7 @@
   }
   uint32 delay = TimeSince(before);
   if (delay >= warn_slow_logs_delay_) {
-    LogMessage slow_log_warning =
-        rtc::LogMessage(__FILE__, __LINE__, LS_WARNING);
+    rtc::LogMessage slow_log_warning(__FILE__, __LINE__, LS_WARNING);
     // If our warning is slow, we don't want to warn about it, because
     // that would lead to inifinite recursion.  So, give a really big
     // number for the delay threshold.