Effects: Add atomic_wp<T>, update setThread.

atomic_wp<T> is used to allow concurrent read and write to the wp<>.
We use this to fix EffectCallback::setThread to resolve multithreaded
access to the wp<T>.

Note that setThread is used for EffectChain migration between
PlaybackThreads; we also need to refine higher level transactional
locking to ensure enable/disable of effect is done consistently
during migration.

Test: basic audio works
Test: atest media_synchronization_tests
Test: AudioEffectTest AudioPreProcessingTest BassBoostTest
Test: EnvReverbTest EqualizerTest LoudnessEnhancerTest
Test: PresetReverbTest VirtualizerTest VisualizerTest
Bug: 161341295
Change-Id: If80ee4373859c832d6fd10fec0385d69064f50c6
diff --git a/media/utils/tests/Android.bp b/media/utils/tests/Android.bp
new file mode 100644
index 0000000..bb413c3
--- /dev/null
+++ b/media/utils/tests/Android.bp
@@ -0,0 +1,19 @@
+cc_test {
+    name: "media_synchronization_tests",
+
+    cflags: [
+        "-Wall",
+        "-Werror",
+        "-Wextra",
+    ],
+
+    shared_libs: [
+        "liblog",
+        "libmediautils",
+        "libutils",
+    ],
+
+    srcs: [
+        "media_synchronization_tests.cpp",
+    ],
+}