[test] Add perfetto initialisation to unittest runner

Bug: v8:12781
Change-Id: I1cf929e1d817ba81d25ba5095872b975c13f40d3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3683319
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80891}

test/unittests/run-all-unittests.cc

@@ -11,6 +11,10 @@
 #include "src/base/page-allocator.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
+#ifdef V8_USE_PERFETTO
+#include "src/tracing/trace-event.h"
+#endif  // V8_USE_PERFETTO
+
 namespace {
 
 class CppGCEnvironment final : public ::testing::Environment {
@@ -20,6 +24,13 @@ class CppGCEnvironment final : public ::testing::Environment {
     // has to survive as long as the process, so it's ok to leak the allocator
     // here.
     cppgc::InitializeProcess(new v8::base::PageAllocator());
+
+#ifdef V8_USE_PERFETTO
+    // Set up the in-process perfetto backend.
+    perfetto::TracingInitArgs init_args;
+    init_args.backends = perfetto::BackendType::kInProcessBackend;
+    perfetto::Tracing::Initialize(init_args);
+#endif  // V8_USE_PERFETTO
   }
 
   void TearDown() override { cppgc::ShutdownProcess(); }