re-use WebUIs

chrome/browser/ui/webui/gpu_internals_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/gpu_internals_ui.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 72 matching lines @@
 
   // Executes the javascript function |function_name| in the renderer, passing
   // it the argument |value|.
   void CallJavascriptFunction(const std::wstring& function_name,
                               const Value* value);
 
  private:
   scoped_refptr<CrashUploadList> crash_list_;
   bool crash_list_available_;
 
+  // True if observing the GpuDataManager (re-attaching as observer would
+  // DCHECK).
+  bool observing_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuMessageHandler);
 };
 
 ////////////////////////////////////////////////////////////////////////////////
 //
 // GpuMessageHandler
 //
 ////////////////////////////////////////////////////////////////////////////////
 
 GpuMessageHandler::GpuMessageHandler()
-    : crash_list_available_(false) {
+    : crash_list_available_(false),
+      observing_(false) {
   crash_list_ = CrashUploadList::Create(this);
 }
 
 GpuMessageHandler::~GpuMessageHandler() {
   GpuDataManager::GetInstance()->RemoveObserver(this);
   crash_list_->ClearDelegate();
 }
 
 /* BrowserBridge.callAsync prepends a requestID to these messages. */
 void GpuMessageHandler::RegisterMessages() {
@@ skipping 55 matching lines @@
   } else {
     web_ui()->CallJavascriptFunction("browserBridge.onCallAsyncReply",
         *requestId);
   }
 }
 
 void GpuMessageHandler::OnBrowserBridgeInitialized(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();
 }
 
@@ skipping 99 matching lines @@
 ////////////////////////////////////////////////////////////////////////////////
 
 GpuInternalsUI::GpuInternalsUI(content::WebUI* web_ui)
     : WebUIController(web_ui) {
   web_ui->AddMessageHandler(new GpuMessageHandler());
 
   // Set up the chrome://gpu-internals/ source.
   Profile* profile = Profile::FromWebUI(web_ui);
   ChromeURLDataManager::AddDataSource(profile, CreateGpuHTMLSource());
 }