add classes trace_analyzer::Query and TraceAnalyzer to make it easy to search through trace data

base/debug/trace_event.h

Index: base/debug/trace_event.h
diff --git a/base/debug/trace_event.h b/base/debug/trace_event.h
index e7b3f90066ac8631099d0f39a8558ec517b7f810..51ab238b80fddd4ca40f2a429151e459284bc50a 100644
--- a/base/debug/trace_event.h
+++ b/base/debug/trace_event.h
@@ -403,6 +403,10 @@ class BASE_EXPORT TraceValue {
     return value;
   }
 
+  bool is_string() const {
+    return type_ == TRACE_TYPE_STRING || type_ == TRACE_TYPE_STATIC_STRING;
+  }
+
   void AppendAsJSON(std::string* out) const;
 
   Type type() const {
@@ -429,7 +433,7 @@ class BASE_EXPORT TraceValue {
     return value_.as_pointer;
   }
   const char* as_string() const {
-    DCHECK(type_ == TRACE_TYPE_STRING || type_ == TRACE_TYPE_STATIC_STRING);
+    DCHECK(is_string());
     return value_.as_string;
   }
   const char** as_assignable_string() {
@@ -469,6 +473,9 @@ class TraceEvent {
              bool copy);
   ~TraceEvent();
 
+  static const char* GetPhaseStr(TraceEventPhase phase);
+  static TraceEventPhase GetPhase(const char* phase);
+
   // Serialize event data to JSON
   static void AppendEventsAsJSON(const std::vector<TraceEvent>& events,
                                  size_t start,