Build/use constructormagic.h unconditionally.

These macros no longer collide with Chromium since they are prefixed
with RTC_.

BUG=
R=henrikg@webrtc.org

Review URL: https://codereview.webrtc.org/1477013003 .

Cr-Commit-Position: refs/heads/master@{#10801}

webrtc/base/BUILD.gn

@@ -115,6 +115,7 @@ static_library("rtc_base_approved") {
     "byteorder.h",
     "checks.cc",
     "checks.h",
+    "constructormagic.h",
     "criticalsection.cc",
     "criticalsection.h",
     "event.cc",
@@ -162,7 +163,6 @@ static_library("rtc_base_approved") {
     include_dirs = [ "../../webrtc_overrides" ]
   } else {
     sources += [
-      "constructormagic.h",
       "logging.cc",
       "logging.h",
     ]

webrtc/base/base.gyp

@@ -395,7 +395,6 @@
             'bandwidthsmoother.h',
             'bind.h',
             'callback.h',
-            'constructormagic.h',
             'dbus.cc',
             'dbus.h',
             'diskcache_win32.cc',