Test RTC_DCHECK_IS_ON instead of checking DCHECK_ALWAYS_ON everywhere

The former is always defined (by webrtc/base/checks.h) to either 0 or
1, whereas the latter isn't necessarily defined.

This is a re-land of https://codereview.webrtc.org/2384693002, which
broke Chromium. We re-land without changing this CL at all, because
the thing that needed fixing was in Chromium:
https://codereview.chromium.org/2384263004.

NOTRY=true
TBR=ossu@webrtc.org
BUG=webrtc:6451

Review-Url: https://codereview.webrtc.org/2389943003
Cr-Commit-Position: refs/heads/master@{#14508}
diff --git a/webrtc/api/statscollector.cc b/webrtc/api/statscollector.cc
index 4dd5305..766e949 100644
--- a/webrtc/api/statscollector.cc
+++ b/webrtc/api/statscollector.cc
@@ -398,7 +398,7 @@
                                         uint32_t ssrc) {
   RTC_DCHECK(pc_->session()->signaling_thread()->IsCurrent());
   RTC_DCHECK(audio_track != NULL);
-#if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
+#if RTC_DCHECK_IS_ON
   for (const auto& track : local_audio_tracks_)
     RTC_DCHECK(track.first != audio_track || track.second != ssrc);
 #endif
diff --git a/webrtc/api/statstypes.cc b/webrtc/api/statstypes.cc
index eb6b30c..339d5bb 100644
--- a/webrtc/api/statstypes.cc
+++ b/webrtc/api/statstypes.cc
@@ -276,7 +276,7 @@
     case kFloat:
       return value_.float_ == other.value_.float_;
     case kStaticString: {
-#if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
+#if RTC_DCHECK_IS_ON
       if (value_.static_string_ != other.value_.static_string_) {
         RTC_DCHECK(strcmp(value_.static_string_, other.value_.static_string_) !=
                    0)
@@ -306,7 +306,7 @@
     return value_.string_->compare(value) == 0;
   if (type_ != kStaticString)
     return false;
-#if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
+#if RTC_DCHECK_IS_ON
   if (value_.static_string_ != value)
     RTC_DCHECK(strcmp(value_.static_string_, value) != 0)
         << "Duplicate global?";