Split skydb trace into start_tracing and stop_tracing

sky/tools/debugger/prompt/prompt.cc

 // Copyright 2014 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.
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/debug/profiler.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 63 matching lines @@
   }
 
   void OnClose(int connection_id) override {
   }
 
   void OnHttpRequest(
       int connection_id, const net::HttpServerRequestInfo& info) override {
 
     // FIXME: We should use use a fancier lookup system more like what
     // services/http_server/http_server.cc does with AddHandler.
-    if (info.path == "/trace")
-      ToggleTracing(connection_id);
-    else if (info.path == "/reload")
+    if (info.path == "/reload")
       Load(connection_id, url_);
     else if (info.path == "/inspect")
       Inspect(connection_id);
     else if (info.path == "/quit")
       Quit(connection_id);
     else if (info.path == "/load")
       Load(connection_id, info.data);
     else if (info.path == "/start_profiling")
       StartProfiling(connection_id);
     else if (info.path == "/stop_profiling")
       StopProfiling(connection_id);
-    else {
+    else if (info.path == "/start_tracing")
+      StartTracing(connection_id);
+    else if (info.path == "/stop_tracing")
+      StopTracing(connection_id);
+    else
       Help(info.path, connection_id);
-    }
   }
 
   void OnWebSocketRequest(
       int connection_id, const net::HttpServerRequestInfo& info) override {
     Error(connection_id, "OnWebSocketRequest not implemented");
   }
 
   void OnWebSocketMessage(
       int connection_id, const std::string& data) override {
     Error(connection_id, "OnWebSocketMessage not implemented");
   }
 
   void Error(int connection_id, std::string message) {
     web_server_->Send500(connection_id, message);
   }
 
   void Respond(int connection_id, std::string response) {
     // When sending tracing data back over the wire to the client, we can blow
     // through the default send buffer size.
     web_server_->SetSendBufferSize(
         connection_id, std::max(kMinSendBufferSize, response.length()));
     web_server_->Send200(connection_id, response, "text/plain");
   }
 
   void Help(std::string path, int connection_id) {
     std::string help = base::StringPrintf("Sky Debugger running on port %d\n"
         "Supported URLs:\n"
-        "/toggle_tracing   -- Start/stop tracing\n"
         "/reload           -- Reload the current page\n"
-        "/inspect          -- Start inspector server for current page\n"
         "/quit             -- Quit\n"
         "/load             -- Load a new URL, url in POST body.\n",
         command_port_);
     if (path != "/")
       help = "Unknown path: " + path + "\n\n" + help;
     Respond(connection_id, help);
   }
 
   void Load(int connection_id, std::string url) {
     url_ = url;
@@ skipping 10 matching lines @@
     debugger_->InjectInspector();
     Respond(connection_id,
         "Open the following URL in Chrome:\n"
         "chrome-devtools://devtools/bundled/devtools.html?ws=localhost:9898\n");
   }
 
   void Quit(int connection_id) {
     debugger_->Shutdown();
   }
 
-  void ToggleTracing(int connection_id) {
-    bool was_tracing = is_tracing_;
-    is_tracing_ = !is_tracing_;
-
-    if (was_tracing) {
-      tracing_->StopAndFlush();
-      trace_collector_->GetTrace(base::Bind(
-          &Prompt::OnTraceAvailable, base::Unretained(this), connection_id));
+  void StartTracing(int connection_id) {
+    if (is_tracing_) {
+      Error(connection_id, "Already tracing. Use stop_tracing to stop.\n");
       return;
     }
 
+    is_tracing_ = true;

[eseidel, 2015/01/27 21:07:21]

You don't need to check this, there are apis to tell if we're tracing last I
knew.

[abarth-chromium, 2015/01/27 21:27:59]

We're using mojo's multiapp tracing system to trace all the DLLs at once.

     mojo::DataPipe pipe;
     tracing_->Start(pipe.producer_handle.Pass(), mojo::String("*"));
     trace_collector_.reset(new TraceCollector(pipe.consumer_handle.Pass()));
     Respond(connection_id, "Starting trace (type 'trace' to stop tracing)\n");

[esprehn, 2015/01/27 20:59:24]

is this right? Or do you need to type stop_tracing to stop?

[abarth-chromium, 2015/01/27 21:27:59]

Ah, will fix.

   }
 
+  void StopTracing(int connection_id) {
+    if (!is_tracing_) {
+      Error(connection_id, "Not tracing yet. Use start_tracing to start.\n");
+      return;
+    }
+
+    is_tracing_ = false;
+    tracing_->StopAndFlush();
+    trace_collector_->GetTrace(base::Bind(
+        &Prompt::OnTraceAvailable, base::Unretained(this), connection_id));
+  }
+
   void OnTraceAvailable(int connection_id, std::string trace) {
     trace_collector_.reset();
     Respond(connection_id, trace);
   }
 
   void StartProfiling(int connection_id) {
 #if !defined(NDEBUG) || !defined(ENABLE_PROFILING)
     Error(connection_id,
           "Profiling requires is_debug=false and enable_profiling=true");
     return;
@@ skipping 26 matching lines @@
 };
 
 }  // namespace debugger
 }  // namespace sky
 
 MojoResult MojoMain(MojoHandle shell_handle) {
   mojo::ApplicationRunnerChromium runner(new sky::debugger::Prompt);
   runner.set_message_loop_type(base::MessageLoop::TYPE_IO);
   return runner.Run(shell_handle);
 }