Split PerfDataReader

Split PerfDataReader into two classes, one that does buffering and one
that does the reading.

This way we can later reuse the reading bit in the parser code.

Bug: b/334978369

Change-Id: Icb48d2d7c827df65ff1b4e13056f4d823f28fed4
diff --git a/Android.bp b/Android.bp
index c43694e..ecc4362 100644
--- a/Android.bp
+++ b/Android.bp
@@ -12236,6 +12236,7 @@
     srcs: [
         "src/trace_processor/importers/perf/perf_data_reader_unittest.cc",
         "src/trace_processor/importers/perf/perf_data_tracker_unittest.cc",
+        "src/trace_processor/importers/perf/reader_unittest.cc",
     ],
 }
 
@@ -13333,6 +13334,14 @@
     ],
 }
 
+// GN: //src/trace_processor/util:file_buffer
+filegroup {
+    name: "perfetto_src_trace_processor_util_file_buffer",
+    srcs: [
+        "src/trace_processor/util/file_buffer.cc",
+    ],
+}
+
 // GN: //src/trace_processor/util:glob
 filegroup {
     name: "perfetto_src_trace_processor_util_glob",
@@ -13428,6 +13437,7 @@
     srcs: [
         "src/trace_processor/util/bump_allocator_unittest.cc",
         "src/trace_processor/util/debug_annotation_parser_unittest.cc",
+        "src/trace_processor/util/file_buffer_unittest.cc",
         "src/trace_processor/util/glob_unittest.cc",
         "src/trace_processor/util/gzip_utils_unittest.cc",
         "src/trace_processor/util/proto_profiler_unittest.cc",
@@ -15012,6 +15022,7 @@
         ":perfetto_src_trace_processor_util_build_id",
         ":perfetto_src_trace_processor_util_bump_allocator",
         ":perfetto_src_trace_processor_util_descriptors",
+        ":perfetto_src_trace_processor_util_file_buffer",
         ":perfetto_src_trace_processor_util_glob",
         ":perfetto_src_trace_processor_util_gzip",
         ":perfetto_src_trace_processor_util_interned_message_view",