Background tracing: Added trace_chance

content/browser/tracing/background_tracing_manager_impl.cc

Index: content/browser/tracing/background_tracing_manager_impl.cc
diff --git a/content/browser/tracing/background_tracing_manager_impl.cc b/content/browser/tracing/background_tracing_manager_impl.cc
index 21d6125b788d6f955b14abdd767a639fb0de19a8..5f1e8df0766e2ff692d4782540ea077c176cda0a 100644
--- a/content/browser/tracing/background_tracing_manager_impl.cc
+++ b/content/browser/tracing/background_tracing_manager_impl.cc
@@ -9,6 +9,7 @@
 #include "base/json/json_writer.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/rand_util.h"
 #include "base/sys_info.h"
 #include "base/time/time.h"
 #include "content/browser/tracing/background_tracing_rule.h"
@@ -314,6 +315,13 @@ void BackgroundTracingManagerImpl::OnRuleTriggered(
     StartedFinalizingCallback callback) {
   CHECK(config_);
 
+  double trigger_chance = triggered_rule->trigger_chance();
+  if (trigger_chance < 1.0 && base::RandDouble() > trigger_chance) {
+    if (!callback.is_null())
+      callback.Run(false);
+    return;
+  }
+
   int trace_timeout = triggered_rule->GetTraceTimeout();
 
   if (config_->tracing_mode() == BackgroundTracingConfigImpl::REACTIVE) {