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

chrome/test/automation/browser_proxy.cc

Index: chrome/test/automation/browser_proxy.cc
diff --git a/chrome/test/automation/browser_proxy.cc b/chrome/test/automation/browser_proxy.cc
index a3a1399194c1c8bd66c3324746598f9441943903..9bf31a09026c4d879d81c87b2e51b5f2d201650d 100644
--- a/chrome/test/automation/browser_proxy.cc
+++ b/chrome/test/automation/browser_proxy.cc
@@ -639,3 +639,44 @@ bool BrowserProxy::GetInitialLoadTimes(float* min_start_time,
   std::sort(stop_times->begin(), stop_times->end());
   return true;
 }
+
+bool BrowserProxy::BeginTracing(const std::string& included_categories) {
+  std::vector<std::string> included, excluded;
+  included.push_back(included_categories);
+  return BeginTracing(included, excluded);
+}
+
+bool BrowserProxy::BeginTracing(
+    const std::vector<std::string>& included_categories,
+    const std::vector<std::string>& excluded_categories) {
+  if (!is_valid())
+    return false;
+
+  bool result = false;
+  sender_->Send(new AutomationMsg_BeginTracing(included_categories,
+                                               excluded_categories,
+                                               &result));
+  return result;
+}
+
+bool BrowserProxy::EndTracing(std::string* json_trace_output) {
+  if (!is_valid())
+    return false;
+
+  json_trace_output->clear();
+  bool success = false;
+  int remaining_chunks = 0;
+  std::string chunk;
+  sender_->Send(new AutomationMsg_EndTracing(&success));
+  if (success) {
+    // workaround IPC payload size limitation by getting chunks.
+    do {
+      sender_->Send(new AutomationMsg_GetTracingOutput(&chunk,
+                                                       &remaining_chunks));
+      *json_trace_output += chunk;
+    } while (remaining_chunks > 0);
+    success = (remaining_chunks == 0);
+  }
+  return success;
+}
+