ftrace_reader: Add cpu_reader.cc micro benchmark

Add a micro-benchmark to test the performance of cpu_reader.cc
Also refactor:
- The benchmarking target (so the main lives in benchmark_main.cc)
- The cpu reader test support code (into test/cpu_reader_support.cc)

Change-Id: Ia03df7d9453c098ba3d20d1fc92a95dfc42d678b
diff --git a/Android.bp b/Android.bp
index aca62f5..95237e3 100644
--- a/Android.bp
+++ b/Android.bp
@@ -196,7 +196,9 @@
     "src/ftrace_reader/ftrace_procfs.cc",
     "src/ftrace_reader/ftrace_procfs_integrationtest.cc",
     "src/ftrace_reader/proto_translation_table.cc",
+    "src/ftrace_reader/test/cpu_reader_support.cc",
     "src/ftrace_reader/test/scattered_stream_delegate_for_testing.cc",
+    "src/ftrace_reader/test/scattered_stream_null_delegate.cc",
     "src/ipc/buffered_frame_deserializer.cc",
     "src/ipc/client_impl.cc",
     "src/ipc/deferred.cc",
@@ -1014,7 +1016,9 @@
     "src/ftrace_reader/ftrace_procfs.cc",
     "src/ftrace_reader/proto_translation_table.cc",
     "src/ftrace_reader/proto_translation_table_unittest.cc",
+    "src/ftrace_reader/test/cpu_reader_support.cc",
     "src/ftrace_reader/test/scattered_stream_delegate_for_testing.cc",
+    "src/ftrace_reader/test/scattered_stream_null_delegate.cc",
     "src/ipc/buffered_frame_deserializer.cc",
     "src/ipc/buffered_frame_deserializer_unittest.cc",
     "src/ipc/client_impl.cc",