GN: Refactor modules_unittests to eliminate package boundary violations.

Also move bwe_simulator to webrtc/modules/remote_bitrate_estimator

BUG=webrtc:6954
NOTRY=True

Review-Url: https://codereview.webrtc.org/2649563002
Cr-Commit-Position: refs/heads/master@{#16270}

webrtc/modules/audio_coding/BUILD.gn

@@ -1139,6 +1139,50 @@ if (rtc_include_tests) {
     }
   }
 
+  rtc_source_set("audio_coding_modules_tests") {
+    testonly = true
+    sources = [
+      "test/APITest.cc",
+      "test/Channel.cc",
+      "test/EncodeDecodeTest.cc",
+      "test/PCMFile.cc",
+      "test/PacketLossTest.cc",
+      "test/RTPFile.cc",
+      "test/TestAllCodecs.cc",
+      "test/TestRedFec.cc",
+      "test/TestStereo.cc",
+      "test/TestVADDTX.cc",
+      "test/Tester.cc",
+      "test/TwoWayCommunication.cc",
+      "test/iSACTest.cc",
+      "test/opus_test.cc",
+      "test/target_delay_unittest.cc",
+      "test/utility.cc",
+    ]
+    deps = [
+      ":audio_coding",
+      ":audio_format_conversion",
+      ":builtin_audio_decoder_factory",
+      ":pcm16b_c",
+      "../..:webrtc_common",
+      "../../base:rtc_base_approved",
+      "../../system_wrappers:system_wrappers",
+      "../../test:fileutils",
+      "../../test:test_support",
+    ]
+    defines = audio_coding_defines
+    if (is_win) {
+      cflags = [
+        # TODO(kjellander): bugs.webrtc.org/261: Fix this warning.
+        "/wd4373",  # virtual function override.
+      ]
+    }
+    if (!build_with_chromium && is_clang) {
+      # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
+      suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
+    }
+  }
+
   rtc_source_set("audio_coding_perf_tests") {
     testonly = true
     sources = [