[tracing] free strdup'd memory

ASAN complained about this on another commit:
https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux64%20ASAN/26688
causing revert: https://chromium-review.googlesource.com/c/v8/v8/+/1162122

Change-Id: I3bb16177be9d49496db024ce92fd4354b12d8cc3
Reviewed-on: https://chromium-review.googlesource.com/1187832Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ali Ijaz Sheikh <ofrobots@google.com>
Cr-Commit-Position: refs/heads/master@{#55412}

src/libplatform/tracing/tracing-controller.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "include/libplatform/v8-tracing.h"
@@ -42,7 +43,20 @@ v8::base::AtomicWord g_category_index = g_num_builtin_categories;
 
 TracingController::TracingController() {}
 
-TracingController::~TracingController() { StopTracing(); }
+TracingController::~TracingController() {
+  StopTracing();
+
+  {
+    // Free memory for category group names allocated via strdup.
+    base::LockGuard<base::Mutex> lock(mutex_.get());
+    for (size_t i = g_category_index - 1; i > g_num_builtin_categories; --i) {
+      const char* group = g_category_groups[i];
+      g_category_groups[i] = nullptr;
+      free(const_cast<char*>(group));
+    }
+    g_category_index = g_num_builtin_categories;
+  }
+}
 
 void TracingController::Initialize(TraceBuffer* trace_buffer) {
   trace_buffer_.reset(trace_buffer);