Background tracing: Added trace_chance

content/browser/tracing/background_tracing_manager_impl.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/tracing/background_tracing_manager_impl.h"
 
 #include "base/command_line.h"
 #include "base/cpu.h"
 #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"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/gpu_data_manager.h"
 #include "content/public/browser/tracing_delegate.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
 #include "gpu/config/gpu_info.h"
@@ skipping 285 matching lines @@
 
   triggered_named_event_handle_ = handle;
   OnRuleTriggered(triggered_rule, callback);
 }
 
 void BackgroundTracingManagerImpl::OnRuleTriggered(
     const BackgroundTracingRule* triggered_rule,
     StartedFinalizingCallback callback) {
   CHECK(config_);
 
+  float trigger_chance = triggered_rule->trigger_chance();
+  if (trigger_chance < 1.0f && base::RandDouble() > trigger_chance) {

[shatch, 2015/10/30 19:17:06]

nit: consistent using float or double?

[oystein (OOO til 10th of July), 2015/10/30 19:24:47]

Done.

+    if (!callback.is_null())
+      callback.Run(false);
+    return;
+  }
+
   int trace_timeout = triggered_rule->GetTraceTimeout();
 
   if (config_->tracing_mode() == BackgroundTracingConfigImpl::REACTIVE) {
     // In reactive mode, a trigger starts tracing, or finalizes tracing
     // immediately if it's already running.
     RecordBackgroundTracingMetric(REACTIVE_TRIGGERED);
 
     if (!is_tracing_) {
       // It was not already tracing, start a new trace.
       EnableRecording(GetCategoryFilterStringForCategoryPreset(
@@ skipping 257 matching lines @@
              "disabled-by-default-toplevel.flow,"
              "disabled-by-default-ipc.flow";
     case BackgroundTracingConfigImpl::CategoryPreset::BLINK_STYLE:
       return "blink_style";
   }
   NOTREACHED();
   return "";
 }
 
 }  // namspace content