Added trace query code and wired tracing through BrowserProxy so tests can run traces.

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..cf78fd0833898592e5f15487971e866cf4f5457f 100644
--- a/base/debug/trace_event.h
+++ b/base/debug/trace_event.h
@@ -97,6 +97,7 @@
 
 #include "build/build_config.h"
 
+#include <map>
 #include <string>
 #include <vector>
 
@@ -311,6 +312,7 @@
 namespace base {
 
 class RefCountedString;
+class Value;
 
 namespace debug {
 
@@ -403,6 +405,10 @@ 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 +435,7 @@ 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() {
@@ -451,6 +457,64 @@ class BASE_EXPORT TraceValue {
   Value value_;
 };
 
+// TestTraceEvent is a more convenient form of the TraceEvent class to make
+// tracing-based tests easier to write.
+struct TestTraceEvent {
+  // PidTid contains a Process ID and Thread ID.
+  struct PidTid {
+    PidTid() : pid(0), tid(0) {}
+    PidTid(int pid, int tid) : pid(pid), tid(tid) {}
+    bool operator< (PidTid rhs) const {
+      if (pid != rhs.pid)
+        return pid < rhs.pid;
+      return tid < rhs.tid;
+    }
+    int pid;
+    int tid;
+  };
+
+  TestTraceEvent();
+  TestTraceEvent(const base::Value* event_value);
+  ~TestTraceEvent();
+
+  // Convert JSON string to array of TestTraceEvent.
+  // |output| is appended with the parsed events.
+  static bool ParseEventsFromJson(const std::string& json,
+                                  std::vector<TestTraceEvent>* output);
+
+  bool operator< (const TestTraceEvent& rhs) const {
+    return timestamp < rhs.timestamp;
+  }
+
+  // Returns duration if it's available.
+  bool GetDuration(double* duration) const;
+
+  // Return the argument value if it exists.
+  bool IsArg(const std::string& name) const;
+  // Return the argument value if it exists and it is a string.
+  bool GetArgAsString(const std::string& name, std::string* arg) const;
+  // Return the argument value if it exists and it is a number.
+  bool GetArgAsNumber(const std::string& name, double* arg) const;
+
+  // Called by TraceAnalyzer to associate two events.
+  void SetAssociatedEvent(TestTraceEvent* event);
+
+  // Process ID and Thread ID.
+  PidTid pid_tid;
+  // Time since epoch in microseconds.
+  // Stored as double to match its JSON representation.
+  double timestamp;
+  TraceEventPhase phase;
+  std::string category;
+  std::string name;
+  // All numbers and bool values from TraceEvent args are cast to double.
+  // bool becomes 1.0 (true) or 0.0 (false).
+  std::map<std::string, double> arg_numbers;
+  std::map<std::string, std::string> arg_strings;
+  // Set by TraceAnalyzer to point between matching BEGIN and END events.
+  const TestTraceEvent* associated_event;
+};
+
 // Output records are "Events" and can be obtained via the
 // OutputCallback whenever the tracing system decides to flush. This
 // can happen at any time, on any thread, or you can programatically