Background tracing: Added trace_chance

content/browser/tracing/background_tracing_rule.h

 // 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.
 
 #ifndef CONTENT_BROWSER_TRACING_BACKGROUND_TRACING_RULE_H_
 #define CONTENT_BROWSER_TRACING_BACKGROUND_TRACING_RULE_H_
 
 #include "content/browser/tracing/background_tracing_config_impl.h"
 #include "content/common/content_export.h"
 
 namespace base {
 class DictionaryValue;
 }  // namespace base
 
 namespace content {
 
 class CONTENT_EXPORT BackgroundTracingRule {
  public:
   BackgroundTracingRule();
   virtual ~BackgroundTracingRule();
 
   virtual void Install() {}
-  virtual void IntoDict(base::DictionaryValue* dict) const = 0;
+  virtual void IntoDict(base::DictionaryValue* dict) const;
+  void Setup(const base::DictionaryValue* dict);
   virtual bool ShouldTriggerNamedEvent(const std::string& named_event) const;
   virtual BackgroundTracingConfigImpl::CategoryPreset GetCategoryPreset() const;
   virtual void OnHistogramTrigger(const std::string& histogram_name) const {}
 
   // Seconds from the rule is triggered to finalization should start.
   virtual int GetTraceTimeout() const;
 
+  // Probability that we should allow a tigger to  happen.
+  double trigger_chance() const { return trigger_chance_; }
+
   static scoped_ptr<BackgroundTracingRule> PreemptiveRuleFromDict(
       const base::DictionaryValue* dict);
 
   static scoped_ptr<BackgroundTracingRule> ReactiveRuleFromDict(
       const base::DictionaryValue* dict,
       BackgroundTracingConfigImpl::CategoryPreset category_preset);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BackgroundTracingRule);
+
+  double trigger_chance_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_TRACING_BACKGROUND_TRACING_RULE_H_