Stop using LOG macros in favor of RTC_ prefixed macros.

This CL has been generated with the following script:

for m in PLOG \
  LOG_TAG \
  LOG_GLEM \
  LOG_GLE_EX \
  LOG_GLE \
  LAST_SYSTEM_ERROR \
  LOG_ERRNO_EX \
  LOG_ERRNO \
  LOG_ERR_EX \
  LOG_ERR \
  LOG_V \
  LOG_F \
  LOG_T_F \
  LOG_E \
  LOG_T \
  LOG_CHECK_LEVEL_V \
  LOG_CHECK_LEVEL \
  LOG
do
  git grep -l $m | xargs sed -i "s,\b$m\b,RTC_$m,g"
done
git checkout rtc_base/logging.h
git cl format

Bug: webrtc:8452
Change-Id: I1a53ef3e0a5ef6e244e62b2e012b864914784600
Reviewed-on: https://webrtc-review.googlesource.com/21325
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20617}
diff --git a/rtc_base/helpers.cc b/rtc_base/helpers.cc
index e62aaf8..b0c8856 100644
--- a/rtc_base/helpers.cc
+++ b/rtc_base/helpers.cc
@@ -110,7 +110,7 @@
 
 bool InitRandom(const char* seed, size_t len) {
   if (!Rng().Init(seed, len)) {
-    LOG(LS_ERROR) << "Failed to init random generator!";
+    RTC_LOG(LS_ERROR) << "Failed to init random generator!";
     return false;
   }
   return true;
@@ -128,12 +128,12 @@
   str->clear();
   // Avoid biased modulo division below.
   if (256 % table_size) {
-    LOG(LS_ERROR) << "Table size must divide 256 evenly!";
+    RTC_LOG(LS_ERROR) << "Table size must divide 256 evenly!";
     return false;
   }
   std::unique_ptr<uint8_t[]> bytes(new uint8_t[len]);
   if (!Rng().Generate(bytes.get(), len)) {
-    LOG(LS_ERROR) << "Failed to generate random string!";
+    RTC_LOG(LS_ERROR) << "Failed to generate random string!";
     return false;
   }
   str->reserve(len);