Internalize JSON chunk management to trace_event.h API.

chrome/browser/ui/webui/tracing_ui.cc

 // Copyright (c) 2011 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 "chrome/browser/ui/webui/tracing_ui.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 45 matching lines @@
   // WebUIMessageHandler implementation.
   virtual WebUIMessageHandler* Attach(WebUI* web_ui);
   virtual void RegisterMessages();
 
   // SelectFileDialog::Listener implementation
   virtual void FileSelected(const FilePath& path, int index, void* params);
   virtual void FileSelectionCanceled(void* params);
 
   // TraceSubscriber implementation.
   virtual void OnEndTracingComplete();
-  virtual void OnTraceDataCollected(const std::string& json_events);
+  virtual void OnTraceDataCollected(const std::string& trace_fragment);
   virtual void OnTraceBufferPercentFullReply(float percent_full);
 
   // Messages.
   void OnTracingControllerInitialized(const ListValue* list);
   void OnBeginTracing(const ListValue* list);
   void OnEndTracingAsync(const ListValue* list);
   void OnBeginRequestBufferPercentFull(const ListValue* list);
   void OnLoadTraceFile(const ListValue* list);
   void OnSaveTraceFile(const ListValue* list);
 
@@ skipping 335 matching lines @@
   }
 }
 
 void TracingMessageHandler::OnEndTracingComplete() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   trace_enabled_ = false;
   web_ui_->CallJavascriptFunction("tracingController.onEndTracingComplete");
 }
 
 void TracingMessageHandler::OnTraceDataCollected(
-    const std::string& json_events) {
+    const std::string& trace_fragment) {
+  std::string json_events;
+  base::debug::TraceResultBuffer trace_buffer_;

[nduca, 2011/10/20 00:28:03]

I wasn't expecting this. Was expecting the trace_buffer to be a member on the
message handler, and for us to only hand the the string to JS at the end. I
realize that might then blow-out JS' string size limits, but it'd be
better-matched to the design.

[jbates, 2011/10/20 22:18:49]

It's better for memory performance to pass these through, so let's keep it as
is.

[nduca, 2011/10/20 23:20:05]

Now that you have an output callback, use that instead. E.g. have a
trace_buffer_, and route the output callback to the ExecuteJavascript. You'll
have to tweak onTraceDataCollected to use strings instead of json objects, but
grab me and I can help you.

[jbates, 2011/10/20 23:55:13]

Since you've spent more time in the javascript side of this system, perhaps this
is a quick followup patch for you? The current code looks clean to me, but maybe
that's because I'm not familiar with the JS-side subtleties that you are
thinking about...

+  trace_buffer_.AddFragment(trace_fragment);
+  trace_buffer_.GetJSON(&json_events);
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   std::string javascript = "tracingController.onTraceDataCollected("
       + json_events + ");";
 
   web_ui_->tab_contents()->render_view_host()->
       ExecuteJavascriptInWebFrame(string16(), UTF8ToUTF16(javascript));
 }
 
 void TracingMessageHandler::OnTraceBufferPercentFullReply(float percent_full) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ skipping 11 matching lines @@
 //
 ////////////////////////////////////////////////////////////////////////////////
 
 TracingUI::TracingUI(TabContents* contents) : ChromeWebUI(contents) {
   AddMessageHandler((new TracingMessageHandler())->Attach(this));
 
   // Set up the chrome://tracing/ source.
   Profile::FromBrowserContext(contents->browser_context())->
       GetChromeURLDataManager()->AddDataSource(CreateTracingHTMLSource());
 }