Revert "Remove WEBRTC_TRACE."

This reverts commit 2209b90449473e1df3e0797b6271c7624b41907d.

Reason for revert: breaks Chromium

Original change's description:
> Remove WEBRTC_TRACE.
> 
> Bug: webrtc:5118
> Change-Id: I0af0f8845ee016fa61d7cecc526e2a672ec8732d
> Reviewed-on: https://webrtc-review.googlesource.com/5382
> Reviewed-by: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Commit-Queue: Fredrik Solenberg <solenberg@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#20114}

TBR=solenberg@webrtc.org,sakal@webrtc.org,kwiberg@webrtc.org,nisse@webrtc.org

Change-Id: Ie54fc05c1d7895c088cba410ed87a7c9a0701427
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:5118
Reviewed-on: https://webrtc-review.googlesource.com/5980
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Commit-Queue: Fredrik Solenberg <solenberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20115}
diff --git a/modules/audio_coding/test/EncodeDecodeTest.cc b/modules/audio_coding/test/EncodeDecodeTest.cc
index c765f68..2b6b4ac 100644
--- a/modules/audio_coding/test/EncodeDecodeTest.cc
+++ b/modules/audio_coding/test/EncodeDecodeTest.cc
@@ -19,6 +19,7 @@
 #include "modules/audio_coding/codecs/audio_format_conversion.h"
 #include "modules/audio_coding/include/audio_coding_module.h"
 #include "modules/audio_coding/test/utility.h"
+#include "system_wrappers/include/trace.h"
 #include "test/gtest.h"
 #include "test/testsupport/fileutils.h"
 
@@ -175,6 +176,9 @@
 void Receiver::Teardown() {
   delete[] _playoutBuffer;
   _pcmFile.Close();
+  if (testMode > 1) {
+    Trace::ReturnTrace();
+  }
 }
 
 bool Receiver::IncomingPacket() {
@@ -250,6 +254,9 @@
 
 EncodeDecodeTest::EncodeDecodeTest() {
   _testMode = 2;
+  Trace::CreateTrace();
+  Trace::SetTraceFile(
+      (webrtc::test::OutputPath() + "acm_encdec_trace.txt").c_str());
 }
 
 EncodeDecodeTest::EncodeDecodeTest(int testMode) {
@@ -257,6 +264,11 @@
   //testMode == 1 for testing all codecs/parameters
   //testMode > 1 for specific user-input test (as it was used before)
   _testMode = testMode;
+  if (_testMode != 0) {
+    Trace::CreateTrace();
+    Trace::SetTraceFile(
+        (webrtc::test::OutputPath() + "acm_encdec_trace.txt").c_str());
+  }
 }
 
 void EncodeDecodeTest::Perform() {
@@ -314,6 +326,11 @@
       rtpFile.Close();
     }
   }
+
+  // End tracing.
+  if (_testMode == 1) {
+    Trace::ReturnTrace();
+  }
 }
 
 std::string EncodeDecodeTest::EncodeToFile(int fileType,