Telemetry / Devtools TraceHandler: exposes tracing via dev tools.

content/browser/debugger/devtools_http_handler_impl.cc

Index: content/browser/debugger/devtools_http_handler_impl.cc
diff --git a/content/browser/debugger/devtools_http_handler_impl.cc b/content/browser/debugger/devtools_http_handler_impl.cc
index 377ec1c164bb0714f4e2194ae7ca6f7f813f4818..7f4a7d20e8581b7bf915f7c8c1f7fdd34af99291 100644
--- a/content/browser/debugger/devtools_http_handler_impl.cc
+++ b/content/browser/debugger/devtools_http_handler_impl.cc
@@ -308,6 +308,18 @@ void DevToolsHttpHandlerImpl::OnHttpRequest(
     return;
   }
 
+  if (info.path.find("/trace/") == 0) {
+    // Trace request.
+    BrowserThread::PostTask(
+        BrowserThread::UI,
+        FROM_HERE,
+        base::Bind(&DevToolsHttpHandlerImpl::OnTraceRequestUI,
+                   this,
+                   connection_id,
+                   info));
+    return;
+  }
+
   if (info.path == "" || info.path == "/") {
     // Discovery page request.
     BrowserThread::PostTask(
@@ -578,6 +590,41 @@ void DevToolsHttpHandlerImpl::OnThumbnailRequestUI(
     Send404(connection_id);
 }
 
+void DevToolsHttpHandlerImpl::OnTraceRequestUI(
+    int connection_id,
+    const net::HttpServerRequestInfo& info) {
+  std::string prefix = "/trace/";
+  size_t pos = info.path.find(prefix);

[pfeldman, 2012/12/12 17:45:22]

This discovery handler is supposed to be used with the remote debugging
protocol. Tracing has nothing to do with the devtools at the moment. I would not
want this handler to become a collection of random instrumentations accessible
via web sockets.

+  if (pos != 0) {
+    Send404(connection_id);
+    return;
+  }
+
+  std::string command = info.path.substr(prefix.length());
+
+  std::string response("ok");
+  if (command == "start") {
+    // TODO(bulach): capture categories somehow.
+    std::string categories;
+    devtools_trace_handler_.BeginTracing(categories);
+  } else if (command == "stop")
+    devtools_trace_handler_.EndTracingAsync();
+  else if (command == "has_completed") {
+    response = devtools_trace_handler_.has_completed() ?
+        "ok" : "pending";
+  } else if (command == "get") {
+    if (devtools_trace_handler_.has_completed()) {
+      Send200(
+          connection_id, devtools_trace_handler_.GetAndResetTrace(),
+          "binary/octet-stream");
+      return;
+    }
+    Send404(connection_id);
+    return;
+  }
+  Send200(connection_id, response, "text/html; charset=UTF-8");
+}
+
 void DevToolsHttpHandlerImpl::OnDiscoveryPageRequestUI(int connection_id) {
   std::string response = delegate_->GetDiscoveryPageHTML();
   Send200(connection_id, response, "text/html; charset=UTF-8");