[aapt2] Change the base timestamp of the traces

Perfetto UI doesn't work well if the timestamps are way into
the 64 bit territory. This CL ensures we always start with 0,
making the UI work well for all traces

Bug: 294025081
Test: manual tracing run
Change-Id: I5b74d4dda62ff40c1eab7e33144533e77e59c949

1 files changed, 9 insertions, 5 deletions

diff --git a/tools/aapt2/trace/TraceBuffer.cpp b/tools/aapt2/trace/TraceBuffer.cpp
index fab2df383e3f..0988c313b65b 100644
--- a/tools/aapt2/trace/TraceBuffer.cpp
+++ b/tools/aapt2/trace/TraceBuffer.cpp
@@ -44,14 +44,16 @@ struct TracePoint {
 
 std::vector<TracePoint> traces;
 bool enabled = true;
+constinit std::chrono::steady_clock::time_point startTime = {};
 
 int64_t GetTime() noexcept {
   auto now = std::chrono::steady_clock::now();
-  return std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()).count();
+  if (startTime == decltype(tracebuffer::startTime){}) {
+    startTime = now;
+  }
+  return std::chrono::duration_cast<std::chrono::microseconds>(now - startTime).count();
 }
 
-} // namespace anonymous
-
 void AddWithTime(std::string tag, char type, int64_t time) noexcept {
   TracePoint t = {type, getpid(), time, std::move(tag)};
   traces.emplace_back(std::move(t));
@@ -76,7 +78,7 @@ void Flush(const std::string& basePath) {
 
   // Wrap the trace in a JSON array [] to make Chrome/Perfetto UI handle it.
   char delimiter = '[';
-  for(const TracePoint& trace : traces) {
+  for (const TracePoint& trace : traces) {
     fprintf(f,
             "%c{\"ts\" : \"%" PRIu64
             "\", \"ph\" : \"%c\", \"tid\" : \"%d\" , \"pid\" : \"%d\", \"name\" : \"%s\" }\n",
@@ -90,6 +92,8 @@ void Flush(const std::string& basePath) {
   traces.clear();
 }
 
+}  // namespace
+
 } // namespace tracebuffer
 
 void BeginTrace(std::string tag) {
@@ -166,7 +170,7 @@ FlushTrace::FlushTrace(std::string_view basepath, std::string_view tag,
 
 FlushTrace::~FlushTrace() {
   if (!tracebuffer::enabled) return;
-  tracebuffer::Add(tag_, tracebuffer::kEnd);
+  tracebuffer::Add(std::move(tag_), tracebuffer::kEnd);
   tracebuffer::Flush(basepath_);
 }