Perfetto Client API (1): initial refactorings

This CL lays the grounds for building the client API.
This CL is all about super boring details, to make
next reviews less painful.

Bug: 132678367
Change-Id: I530010631d4c5bd9291fc7f087a51a3cb73b09f6
diff --git a/Android.bp b/Android.bp
index d95ab75..f962ee2 100644
--- a/Android.bp
+++ b/Android.bp
@@ -97,6 +97,7 @@
     "src/protozero/scattered_heap_buffer.cc",
     "src/protozero/scattered_stream_null_delegate.cc",
     "src/protozero/scattered_stream_writer.cc",
+    "src/public/trace_writer_base.cc",
     "src/tracing/core/chrome_config.cc",
     "src/tracing/core/commit_data_request.cc",
     "src/tracing/core/data_source_config.cc",
@@ -263,6 +264,7 @@
     "src/protozero/scattered_heap_buffer.cc",
     "src/protozero/scattered_stream_null_delegate.cc",
     "src/protozero/scattered_stream_writer.cc",
+    "src/public/trace_writer_base.cc",
     "src/traced/probes/android_log/android_log_data_source.cc",
     "src/traced/probes/filesystem/file_scanner.cc",
     "src/traced/probes/filesystem/fs_mount.cc",
@@ -447,6 +449,7 @@
     "src/protozero/scattered_heap_buffer.cc",
     "src/protozero/scattered_stream_null_delegate.cc",
     "src/protozero/scattered_stream_writer.cc",
+    "src/public/trace_writer_base.cc",
     "src/tracing/core/chrome_config.cc",
     "src/tracing/core/commit_data_request.cc",
     "src/tracing/core/data_source_config.cc",
@@ -618,6 +621,7 @@
     "src/protozero/scattered_heap_buffer.cc",
     "src/protozero/scattered_stream_null_delegate.cc",
     "src/protozero/scattered_stream_writer.cc",
+    "src/public/trace_writer_base.cc",
     "src/traced/probes/android_log/android_log_data_source.cc",
     "src/traced/probes/filesystem/file_scanner.cc",
     "src/traced/probes/filesystem/fs_mount.cc",
@@ -2678,6 +2682,7 @@
     "src/protozero/scattered_heap_buffer.cc",
     "src/protozero/scattered_stream_null_delegate.cc",
     "src/protozero/scattered_stream_writer.cc",
+    "src/public/trace_writer_base.cc",
     "src/tracing/core/chrome_config.cc",
     "src/tracing/core/commit_data_request.cc",
     "src/tracing/core/data_source_config.cc",
@@ -2969,6 +2974,7 @@
     "src/protozero/scattered_stream_writer_unittest.cc",
     "src/protozero/test/fake_scattered_buffer.cc",
     "src/protozero/test/protozero_conformance_unittest.cc",
+    "src/public/trace_writer_base.cc",
     "src/traced/probes/android_log/android_log_data_source.cc",
     "src/traced/probes/android_log/android_log_data_source_unittest.cc",
     "src/traced/probes/filesystem/file_scanner.cc",
@@ -3403,6 +3409,7 @@
     "src/protozero/scattered_heap_buffer.cc",
     "src/protozero/scattered_stream_null_delegate.cc",
     "src/protozero/scattered_stream_writer.cc",
+    "src/public/trace_writer_base.cc",
     "src/tracing/core/chrome_config.cc",
     "src/tracing/core/commit_data_request.cc",
     "src/tracing/core/data_source_config.cc",