re-use WebUIs

chrome/browser/ui/webui/tracing_ui.cc

 // Copyright (c) 2012 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 100 matching lines @@
 
   // The trace data that is to be written to the file on saving.
   scoped_ptr<std::string> trace_data_to_save_;
 
   // True while tracing is active.
   bool trace_enabled_;
 
   // True while system tracing is active.
   bool system_trace_in_progress_;
 
+  // True if observing the GpuDataManager (re-attaching as observer would
+  // DCHECK).
+  bool observing_;
+
   void OnEndSystemTracingAck(
       const scoped_refptr<base::RefCountedString>& events_str_ptr);
 
   DISALLOW_COPY_AND_ASSIGN(TracingMessageHandler);
 };
 
 // A proxy passed to the Read and Write tasks used when loading or saving trace
 // data.
 class TaskProxy : public base::RefCountedThreadSafe<TaskProxy> {
  public:
@@ skipping 22 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 //
 // TracingMessageHandler
 //
 ////////////////////////////////////////////////////////////////////////////////
 
 TracingMessageHandler::TracingMessageHandler()
   : select_trace_file_dialog_type_(SelectFileDialog::SELECT_NONE),
     trace_enabled_(false),
-    system_trace_in_progress_(false) {
+    system_trace_in_progress_(false),
+    observing_(false) {
 }
 
 TracingMessageHandler::~TracingMessageHandler() {
   GpuDataManager::GetInstance()->RemoveObserver(this);
 
   if (select_trace_file_dialog_)
     select_trace_file_dialog_->ListenerDestroyed();
 
   // If we are the current subscriber, this will result in ending tracing.
   TraceController::GetInstance()->CancelSubscriber(this);
@@ skipping 29 matching lines @@
   web_ui()->RegisterMessageCallback("saveTraceFile",
       base::Bind(&TracingMessageHandler::OnSaveTraceFile,
                  base::Unretained(this)));
 }
 
 void TracingMessageHandler::OnTracingControllerInitialized(
     const ListValue* args) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   // Watch for changes in GPUInfo
-  GpuDataManager::GetInstance()->AddObserver(this);
+  if (!observing_)
+    GpuDataManager::GetInstance()->AddObserver(this);
+  observing_ = true;
 
   // Tell GpuDataManager it should have full GpuInfo. If the
   // Gpu process has not run yet, this will trigger its launch.
   GpuDataManager::GetInstance()->RequestCompleteGpuInfoIfNeeded();
 
   // Run callback immediately in case the info is ready and no update in the
   // future.
   OnGpuInfoUpdate();
 
   // Send the client info to the tracingController
@@ skipping 258 matching lines @@
 //
 ////////////////////////////////////////////////////////////////////////////////
 
 TracingUI::TracingUI(content::WebUI* web_ui) : WebUIController(web_ui) {
   web_ui->AddMessageHandler(new TracingMessageHandler());
 
   // Set up the chrome://tracing/ source.
   Profile* profile = Profile::FromWebUI(web_ui);
   ChromeURLDataManager::AddDataSource(profile, CreateTracingHTMLSource());
 }