client: Add logging callback for log redirection.

SetLogMessageCallback allows callers to intercept log messages
after formatting. The log message callback can also be specified
in TracingInitArgs.

Change-Id: I0f4192acc57b0edb5c8269a6f62ad46fe9304948
diff --git a/Android.bp b/Android.bp
index d891e49..a69fc2c 100644
--- a/Android.bp
+++ b/Android.bp
@@ -6697,6 +6697,7 @@
     "src/base/circular_queue_unittest.cc",
     "src/base/flat_set_unittest.cc",
     "src/base/getopt_compat_unittest.cc",
+    "src/base/logging_unittest.cc",
     "src/base/metatrace_unittest.cc",
     "src/base/no_destructor_unittest.cc",
     "src/base/optional_unittest.cc",