Fix bug causing tab favicon media indicator to not turn off.

chrome/browser/media/media_stream_capture_indicator.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/media/media_stream_capture_indicator.h"
 
 #include "base/bind.h"
 #include "base/i18n/rtl.h"
 #include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/image_loader.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/status_icons/status_icon.h"
 #include "chrome/browser/status_icons/status_tray.h"
 #include "chrome/browser/tab_contents/tab_util.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/invalidate_type.h"
-#include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_delegate.h"
-#include "content/public/common/media_stream_request.h"
 #include "grit/chromium_strings.h"
 #include "grit/generated_resources.h"
 #include "grit/theme_resources.h"
 #include "net/base/net_util.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/image/image_skia.h"
 
 using content::BrowserThread;
 using content::WebContents;
 
 namespace {
 
-const extensions::Extension* GetExtension(int render_process_id,
-                                          int render_view_id) {
+const extensions::Extension* GetExtension(WebContents* web_contents) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  WebContents* web_contents = tab_util::GetWebContentsByID(
-      render_process_id, render_view_id);
   if (!web_contents)
     return NULL;
 
   Profile* profile =
       Profile::FromBrowserContext(web_contents->GetBrowserContext());
   if (!profile)
     return NULL;
 
   ExtensionService* extension_service = profile->GetExtensionService();
   if (!extension_service)
     return NULL;
 
   return extension_service->extensions()->GetExtensionOrAppByURL(
       ExtensionURLInfo(web_contents->GetURL()));
 }
 
 // Gets the security originator of the tab. It returns a string with no '/'
 // at the end to display in the UI.
-string16 GetSecurityOrigin(int render_process_id, int render_view_id) {
+string16 GetSecurityOrigin(WebContents* web_contents) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  WebContents* tab_content = tab_util::GetWebContentsByID(
-      render_process_id, render_view_id);
-  if (!tab_content)
+
+  if (!web_contents)
     return string16();
 
-  std::string security_origin = tab_content->GetURL().GetOrigin().spec();
+  std::string security_origin = web_contents->GetURL().GetOrigin().spec();
 
   // Remove the last character if it is a '/'.
   if (!security_origin.empty()) {
     std::string::iterator it = security_origin.end() - 1;
     if (*it == '/')
       security_origin.erase(it);
   }
 
   return UTF8ToUTF16(security_origin);
 }
 
-string16 GetTitle(int render_process_id, int render_view_id) {
+string16 GetTitle(WebContents* web_contents) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  const extensions::Extension* extension =
-      GetExtension(render_process_id, render_view_id);
+  if (!web_contents)
+    return string16();
+
+  const extensions::Extension* const extension = GetExtension(web_contents);
   if (extension)
     return UTF8ToUTF16(extension->name());
 
-  WebContents* tab_content = tab_util::GetWebContentsByID(
-      render_process_id, render_view_id);
-  if (!tab_content)
-    return string16();
-
-  string16 tab_title = tab_content->GetTitle();
+  string16 tab_title = web_contents->GetTitle();
 
   if (tab_title.empty()) {
     // If the page's title is empty use its security originator.
-    tab_title = GetSecurityOrigin(render_process_id, render_view_id);
+    tab_title = GetSecurityOrigin(web_contents);
   } else {
     // If the page's title matches its URL, use its security originator.
     std::string languages =
         content::GetContentClient()->browser()->GetAcceptLangs(
-            tab_content->GetBrowserContext());
-    if (tab_title == net::FormatUrl(tab_content->GetURL(), languages))
-      tab_title = GetSecurityOrigin(render_process_id, render_view_id);
+            web_contents->GetBrowserContext());
+    if (tab_title == net::FormatUrl(web_contents->GetURL(), languages))
+      tab_title = GetSecurityOrigin(web_contents);
   }
 
   return tab_title;
 }
 
+void CountDevices(const content::MediaStreamDevices& devices,
+                  int* num_audio, int* num_video, int* num_mirroring) {
+  for (content::MediaStreamDevices::const_iterator it = devices.begin();
+       it != devices.end(); ++it) {
+    if (it->type == content::MEDIA_TAB_AUDIO_CAPTURE ||
+        it->type == content::MEDIA_TAB_VIDEO_CAPTURE) {
+      ++(*num_mirroring);
+    } else if (content::IsAudioMediaType(it->type)) {
+      ++(*num_audio);
+    } else if (content::IsVideoMediaType(it->type)) {
+      ++(*num_video);
+    } else {
+      NOTIMPLEMENTED();
+    }
+  }
+}
+
 }  // namespace
 
-MediaStreamCaptureIndicator::TabEquals::TabEquals(WebContents* web_contents,
-                                                  int render_process_id,
-                                                  int render_view_id)
-    : web_contents_(web_contents),
-      render_process_id_(render_process_id),
-      render_view_id_(render_view_id) {}
+// Stores usage counts for all the capture devices associated with a single
+// WebContents instance.
+class MediaStreamCaptureIndicator::CaptureDeviceUsage {
+ public:
+  CaptureDeviceUsage();
 
-bool MediaStreamCaptureIndicator::TabEquals::operator() (
-    const MediaStreamCaptureIndicator::CaptureDeviceTab& tab) {
-  return (web_contents_ == tab.web_contents ||
-          (render_process_id_ == tab.render_process_id &&
-           render_view_id_ == tab.render_view_id));
+  bool IsCapturingAudio() const { return audio_ref_count_ > 0; }
+  bool IsCapturingVideo() const { return video_ref_count_ > 0; }
+  bool IsMirroring() const { return mirroring_ref_count_ > 0; }
+
+  void TallyUsage(int num_audio, int num_video, int num_mirroring);
+
+ private:
+  int audio_ref_count_;
+  int video_ref_count_;
+  int mirroring_ref_count_;
+};
+
+MediaStreamCaptureIndicator::CaptureDeviceUsage::CaptureDeviceUsage()
+    : audio_ref_count_(0), video_ref_count_(0), mirroring_ref_count_(0) {
+}
+
+void MediaStreamCaptureIndicator::CaptureDeviceUsage::TallyUsage(
+    int num_audio, int num_video, int num_mirroring) {
+  audio_ref_count_ += num_audio;
+  DCHECK_LE(0, audio_ref_count_);
+  video_ref_count_ += num_video;
+  DCHECK_LE(0, video_ref_count_);
+  mirroring_ref_count_ += num_mirroring;
+  DCHECK_LE(0, mirroring_ref_count_);
 }
 
 MediaStreamCaptureIndicator::MediaStreamCaptureIndicator()
     : status_icon_(NULL),
       mic_image_(NULL),
       camera_image_(NULL),
       balloon_image_(NULL),
       should_show_balloon_(false) {
 }
 
 MediaStreamCaptureIndicator::~MediaStreamCaptureIndicator() {
-  // The user is responsible for cleaning up by closing all the opened devices.
-  DCHECK(tabs_.empty());

[no longer working on chromium, 2013/01/24 14:09:06]

please add back DCHECKs for aliases_ and usage_map. If they are not empty, it
might mean the UI is leaking. We prefer having the browser crash rather than
showing a wrong UI.

[miu, 2013/01/28 19:36:52]

Done.  Originally, I thought this was an issue only upon shutdown (where
MediaStreamCaptureIndicator is unhooked and destroyed before all "close" events
are sent to it).  Seems to be all fixed now.  :)

 }
 
 bool MediaStreamCaptureIndicator::IsCommandIdChecked(
     int command_id) const {
   NOTIMPLEMENTED() << "There are no checked items in the MediaStream menu.";
   return false;
 }
 
 bool MediaStreamCaptureIndicator::IsCommandIdEnabled(
     int command_id) const {
   return command_id != IDC_MinimumLabelValue;
 }
 
 bool MediaStreamCaptureIndicator::GetAcceleratorForCommandId(
     int command_id, ui::Accelerator* accelerator) {
   // No accelerators for status icon context menu.
   return false;
 }
 
 void MediaStreamCaptureIndicator::ExecuteCommand(int command_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK(command_id >= IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_FIRST &&
-         command_id <= IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_LAST);
-  int index = command_id - IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_FIRST;
-  WebContents* web_content = tab_util::GetWebContentsByID(
-      tabs_[index].render_process_id, tabs_[index].render_view_id);
-  DCHECK(web_content);
-  if (!web_content) {
+
+  const int index =

[no longer working on chromium, 2013/01/24 14:09:06]

nit, you don't need const for int.

[miu, 2013/01/28 19:36:52]

Ack.  IMHO, it's a good habit to use const wherever possible to catch bugs. 
This is one of those things the style guide says to do, but many people forget
(see
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Use_of_const).

Also, if you have a few minutes, here's a very funny (and educational) video
clip: http://gamesfromwithin.com/the-const-nazi

Granted, it's use here is a bit pedantic, but why take it out?

+      command_id - IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_FIRST;
+  DCHECK_LE(0, index);
+  DCHECK_GT(static_cast<int>(command_map_.size()), index);
+  WebContents* const web_contents = command_map_[index];
+  if (!web_contents) {
     NOTREACHED();
     return;
   }
 
-  web_content->GetDelegate()->ActivateContents(web_content);
+  web_contents->GetDelegate()->ActivateContents(web_contents);
 }
 
 void MediaStreamCaptureIndicator::CaptureDevicesOpened(
     int render_process_id,
     int render_view_id,
     const content::MediaStreamDevices& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   DCHECK(!devices.empty());
 
   BrowserThread::PostTask(
@@ skipping 14 matching lines @@
       base::Bind(&MediaStreamCaptureIndicator::DoDevicesClosedOnUIThread,
                  this, render_process_id, render_view_id, devices));
 }
 
 void MediaStreamCaptureIndicator::DoDevicesOpenedOnUIThread(
     int render_process_id,
     int render_view_id,
     const content::MediaStreamDevices& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  CreateStatusTray();
-
-  AddCaptureDeviceTab(render_process_id, render_view_id, devices);
+  AddCaptureDevices(render_process_id, render_view_id, devices);
 }
 
 void MediaStreamCaptureIndicator::DoDevicesClosedOnUIThread(
     int render_process_id,
     int render_view_id,
     const content::MediaStreamDevices& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  RemoveCaptureDeviceTab(render_process_id, render_view_id, devices);
+  RemoveCaptureDevices(render_process_id, render_view_id, devices);
 }
 
-void MediaStreamCaptureIndicator::CreateStatusTray() {
+void MediaStreamCaptureIndicator::MaybeCreateStatusTrayIcon() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   if (status_icon_)
     return;
 
   // If there is no browser process, we should not create the status tray.
   if (!g_browser_process)
     return;
 
   StatusTray* status_tray = g_browser_process->status_tray();
   if (!status_tray)
@@ skipping 17 matching lines @@
   if (!balloon_image_) {
     balloon_image_ = ResourceBundle::GetSharedInstance().GetImageSkiaNamed(
         IDR_PRODUCT_LOGO_32);
   }
   DCHECK(mic_image_);
   DCHECK(camera_image_);
   DCHECK(balloon_image_);
 }
 
 void MediaStreamCaptureIndicator::ShowBalloon(
-    int render_process_id,
-    int render_view_id,
-    bool audio,
-    bool video) {
+    WebContents* web_contents, bool audio, bool video) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(audio || video);
 
   int message_id = IDS_MEDIA_STREAM_STATUS_TRAY_BALLOON_BODY_AUDIO_AND_VIDEO;
   if (audio && !video)
     message_id = IDS_MEDIA_STREAM_STATUS_TRAY_BALLOON_BODY_AUDIO_ONLY;
   else if (!audio && video)
     message_id = IDS_MEDIA_STREAM_STATUS_TRAY_BALLOON_BODY_VIDEO_ONLY;
 
   // Only show the balloon for extensions.
-  const extensions::Extension* extension =
-      GetExtension(render_process_id, render_view_id);
+  const extensions::Extension* const extension = GetExtension(web_contents);
   if (!extension) {
     DVLOG(1) << "Balloon is shown only for extensions";
     return;
   }
 
   string16 message =
       l10n_util::GetStringFUTF16(message_id,
                                  UTF8ToUTF16(extension->name()));
-
-  WebContents* web_contents = tab_util::GetWebContentsByID(
-        render_process_id, render_view_id);
-
   Profile* profile =
       Profile::FromBrowserContext(web_contents->GetBrowserContext());
 
   should_show_balloon_ = true;
   extensions::ImageLoader::Get(profile)->LoadImageAsync(
       extension,
       extension->GetIconResource(32, ExtensionIconSet::MATCH_BIGGER),
       gfx::Size(32, 32),
       base::Bind(&MediaStreamCaptureIndicator::OnImageLoaded,
                  this, message));
 }
 
 void MediaStreamCaptureIndicator::OnImageLoaded(
     const string16& message,
     const gfx::Image& image) {
-  if (!should_show_balloon_)
+  if (!should_show_balloon_ || !status_icon_)
     return;
 
   const gfx::ImageSkia* image_skia = !image.IsEmpty() ? image.ToImageSkia() :
       ui::ResourceBundle::GetSharedInstance().GetImageSkiaNamed(
           IDR_APP_DEFAULT_ICON);
   status_icon_->DisplayBalloon(*image_skia, string16(), message);
 }
 
-void MediaStreamCaptureIndicator::Hide() {
+void MediaStreamCaptureIndicator::MaybeDestroyStatusTrayIcon() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   // Make sure images that finish loading don't cause a balloon to be shown.
   should_show_balloon_ = false;
 
   if (!status_icon_)
     return;
 
   // If there is no browser process, we should not do anything.
   if (!g_browser_process)
     return;
 
   StatusTray* status_tray = g_browser_process->status_tray();
   if (status_tray != NULL) {
     status_tray->RemoveStatusIcon(status_icon_);
     status_icon_ = NULL;
   }
 }
 
 void MediaStreamCaptureIndicator::UpdateStatusTrayIconContextMenu() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   scoped_ptr<ui::SimpleMenuModel> menu(new ui::SimpleMenuModel(this));
 
   bool audio = false;
   bool video = false;
   int command_id = IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_FIRST;
-  for (CaptureDeviceTabs::iterator iter = tabs_.begin();
-       iter != tabs_.end();) {
-    string16 tab_title = GetTitle(iter->render_process_id,
-                                  iter->render_view_id);
-    if (tab_title.empty()) {
-      // Delete the entry since the tab has gone away.
-      iter = tabs_.erase(iter);
-      continue;
-    }
+  command_map_.clear();
+  for (UsageMap::const_iterator iter = usage_map_.begin();
+       iter != usage_map_.end(); ++iter) {
+    WebContents* const web_contents = iter->first;
+    command_map_.push_back(web_contents);
+    menu->AddItem(command_id, GetTitle(web_contents));
 
     // Check if any audio and video devices have been used.
-    audio = audio || iter->audio_ref_count > 0;
-    video = video || iter->video_ref_count > 0;
-
-    menu->AddItem(command_id, tab_title);
+    const CaptureDeviceUsage& usage = *iter->second;
+    audio = audio || usage.IsCapturingAudio();
+    video = video || usage.IsCapturingVideo();
 
     // If reaching the maximum number, no more item will be added to the menu.
     if (command_id == IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_LAST)
       break;
-
     ++command_id;
-    ++iter;
   }
 
   if (!audio && !video) {
-    Hide();
+    MaybeDestroyStatusTrayIcon();
     return;
   }
 
   // The icon will take the ownership of the passed context menu.
-  status_icon_->SetContextMenu(menu.release());
-  UpdateStatusTrayIconDisplay(audio, video);
+  MaybeCreateStatusTrayIcon();
+  if (status_icon_) {
+    status_icon_->SetContextMenu(menu.release());
+    UpdateStatusTrayIconDisplay(audio, video);
+  }
 }
 
 void MediaStreamCaptureIndicator::UpdateStatusTrayIconDisplay(
     bool audio, bool video) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(audio || video);
+  DCHECK(status_icon_);
   int message_id = 0;
   if (audio && video) {
     message_id = IDS_MEDIA_STREAM_STATUS_TRAY_TEXT_AUDIO_AND_VIDEO;
     status_icon_->SetImage(*camera_image_);
   } else if (audio && !video) {
     message_id = IDS_MEDIA_STREAM_STATUS_TRAY_TEXT_AUDIO_ONLY;
     status_icon_->SetImage(*mic_image_);
   } else if (!audio && video) {
     message_id = IDS_MEDIA_STREAM_STATUS_TRAY_TEXT_VIDEO_ONLY;
     status_icon_->SetImage(*camera_image_);
   }
 
   status_icon_->SetToolTip(l10n_util::GetStringFUTF16(
       message_id, l10n_util::GetStringUTF16(IDS_PRODUCT_NAME)));
 }
 
-void MediaStreamCaptureIndicator::AddCaptureDeviceTab(
+content::WebContents* MediaStreamCaptureIndicator::LookUpByKnownAlias(
+    int render_process_id, int render_view_id) const {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  WebContents* result =
+      tab_util::GetWebContentsByID(render_process_id, render_view_id);
+  if (!result) {
+    const RenderViewIDs key(render_process_id, render_view_id);
+    AliasMap::const_iterator it = aliases_.find(key);
+    if (it != aliases_.end())
+      result = it->second;
+  }
+  return result;
+}
+
+void MediaStreamCaptureIndicator::AddCaptureDevices(
     int render_process_id,
     int render_view_id,
     const content::MediaStreamDevices& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  WebContents* web_contents = tab_util::GetWebContentsByID(render_process_id,
-                                                           render_view_id);
+  WebContents* const web_contents =
+      LookUpByKnownAlias(render_process_id, render_view_id);
   if (!web_contents)
     return;
 
-  CaptureDeviceTabs::iterator iter = std::find_if(
-      tabs_.begin(), tabs_.end(), TabEquals(web_contents,
-                                            render_process_id,
-                                            render_view_id));
-  if (iter == tabs_.end()) {
-    tabs_.push_back(CaptureDeviceTab(web_contents,
-                                     render_process_id,
-                                     render_view_id));
-    iter = tabs_.end() - 1;
-  }
+  // Increase the usage ref-counts.
+  int num_audio = 0;
+  int num_video = 0;
+  int num_mirroring = 0;
+  CountDevices(devices, &num_audio, &num_video, &num_mirroring);

[justinlin, 2013/01/24 07:04:44]

Could the CountDevices function just be moved into
CaptureDeviceUsage::TallyUsage? We can expose something like a
"ShouldShowDesktopNotifications" method there too.

[no longer working on chromium, 2013/01/24 14:09:06]

+1

[miu, 2013/01/28 19:36:52]

Done.  Good call!  :)

BTW--It seemed cleanest to have TallyUsage() just return the appropriate balloon
body message ID when the balloon is to be shown.

+  DCHECK(num_audio > 0 || num_video > 0 || num_mirroring > 0);
+  CaptureDeviceUsage*& usage = usage_map_[web_contents];
+  if (!usage)
+    usage = new CaptureDeviceUsage();
+  usage->TallyUsage(num_audio, num_video, num_mirroring);
 
-  bool audio = false;
-  bool video = false;
-  bool tab_capture = false;
-  content::MediaStreamDevices::const_iterator dev = devices.begin();
-  for (; dev != devices.end(); ++dev) {
-    if (dev->type == content::MEDIA_TAB_AUDIO_CAPTURE ||
-        dev->type == content::MEDIA_TAB_VIDEO_CAPTURE) {
-      ++iter->tab_capture_ref_count;
-      tab_capture = true;
-    } else if (content::IsAudioMediaType(dev->type)) {
-      ++iter->audio_ref_count;
-      audio = true;
-    } else if (content::IsVideoMediaType(dev->type)) {
-      ++iter->video_ref_count;
-      video = true;
-    } else {
-      NOTIMPLEMENTED();
-    }
-  }
+  // Keep track of the IDs as a known alias to the WebContents instance.
+  const AliasMap::iterator insert_it = aliases_.insert(
+      make_pair(RenderViewIDs(render_process_id, render_view_id),
+                web_contents)).first;
+  DCHECK_EQ(web_contents, insert_it->second)
+      << "BUG: IDs refer to two different WebContents instances.";
 
-  DCHECK(web_contents);
   web_contents->NotifyNavigationStateChanged(content::INVALIDATE_TYPE_TAB);
 
   // Don't use desktop notifications for tab capture. We use a favicon
   // glow notification instead.
-  if (!status_icon_ || tab_capture)
+  if (num_mirroring > 0 && num_audio == 0 && num_video == 0)
     return;
 
   UpdateStatusTrayIconContextMenu();
-  ShowBalloon(render_process_id, render_view_id, audio, video);
+  ShowBalloon(web_contents, num_audio > 0, num_video > 0);
 }
 
-void MediaStreamCaptureIndicator::RemoveCaptureDeviceTab(
+void MediaStreamCaptureIndicator::RemoveCaptureDevices(
     int render_process_id,
     int render_view_id,
     const content::MediaStreamDevices& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  WebContents* web_contents = tab_util::GetWebContentsByID(render_process_id,
-                                                           render_view_id);
-  CaptureDeviceTabs::iterator iter = std::find_if(
-      tabs_.begin(), tabs_.end(), TabEquals(web_contents,
-                                            render_process_id,
-                                            render_view_id));
 
-  if (iter != tabs_.end()) {
-    content::MediaStreamDevices::const_iterator dev = devices.begin();
-    for (; dev != devices.end(); ++dev) {
-      if (dev->type == content::MEDIA_TAB_AUDIO_CAPTURE ||
-          dev->type == content::MEDIA_TAB_VIDEO_CAPTURE) {
-        --iter->tab_capture_ref_count;
-      } else if (content::IsAudioMediaType(dev->type)) {
-        --iter->audio_ref_count;
-      } else if (content::IsVideoMediaType(dev->type)) {
-        --iter->video_ref_count;
+  WebContents* const web_contents =
+      LookUpByKnownAlias(render_process_id, render_view_id);
+  if (!web_contents)
+    return;
+
+  // Decrease the usage ref-counts.
+  int num_audio = 0;
+  int num_video = 0;
+  int num_mirroring = 0;
+  CountDevices(devices, &num_audio, &num_video, &num_mirroring);
+  CaptureDeviceUsage* const usage = usage_map_[web_contents];
+  DCHECK(usage);
+  usage->TallyUsage(-num_audio, -num_video, -num_mirroring);
+
+  // Remove the usage and alias mappings if all the devices have been closed.
+  if (!usage->IsCapturingAudio() && !usage->IsCapturingVideo() &&
+      !usage->IsMirroring()) {
+    for (AliasMap::iterator alias_it = aliases_.begin();
+         alias_it != aliases_.end(); ) {
+      if (alias_it->second == web_contents) {
+        aliases_.erase(alias_it++);
       } else {
-        NOTIMPLEMENTED();
+        ++alias_it;
       }
-
-      DCHECK_GE(iter->audio_ref_count, 0);
-      DCHECK_GE(iter->video_ref_count, 0);
     }
-
-    // Remove the tab if all the devices have been closed.
-    if (iter->audio_ref_count == 0 && iter->video_ref_count == 0 &&
-        iter->tab_capture_ref_count == 0)
-      tabs_.erase(iter);
+    delete usage;
+    usage_map_.erase(web_contents);
   }
 
-  if (web_contents)
-    web_contents->NotifyNavigationStateChanged(content::INVALIDATE_TYPE_TAB);
-
-  if (!status_icon_)
-    return;
+  web_contents->NotifyNavigationStateChanged(content::INVALIDATE_TYPE_TAB);

[no longer working on chromium, 2013/01/24 14:09:06]

what if the page has gone and the web_contents is from aliases_, will it be a
problem for using the cached web_contents here?

Besides, please do a test to verify the UI works in the following case:
Open two tabs with apprtc.appspot.com and
https://webrtc-demos.appspot.com/html/pc1.html; allow the access; open the third
tab, right click and close other tabs.

[no longer working on chromium, 2013/01/24 14:45:55]

Note, you should do the test on Mac or windows 7, since the system tray is not
available on the gprecise and windows 8.

[miu, 2013/01/28 19:36:52]

With all my testing, I never saw this happen.  However, after using xians's test
strategy (which involves using WebRTC functionality), it turns out that a
WebContents *can* be destroyed before the "close" method is called.  I'm
guessing there's some extra thread trampolining causing the out-of-order calls
to MediaStreamCaptureIndicator.

This was easy to cleanly fix, however.  I just use WebContentsObserver to
observe the destroy event, and make sure I only deref the pointer if destruction
has not yet occurred.
Good idea!  This caught the WebContents destroy-before-use bug here in
MediaStreamCaptureIndicator.  I fixed the problem.

Confirmed many tab open/close, start/stop, WebRTC/PPAPI/etc., combinations all
do the right thing.

[miu, 2013/01/28 19:36:52]

Actually, gprecise has the system tray and it was working for me.  I also plan
on testing all this thoroughly on my Win7 desktop before I commit.

 
   UpdateStatusTrayIconContextMenu();
 }
 
-bool MediaStreamCaptureIndicator::IsProcessCapturing(int render_process_id,
-                                                     int render_view_id) const {
+bool MediaStreamCaptureIndicator::IsCapturingUserMedia(
+    int render_process_id, int render_view_id) const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  WebContents* web_contents = tab_util::GetWebContentsByID(render_process_id,
-                                                           render_view_id);
+
+  WebContents* const web_contents =
+      LookUpByKnownAlias(render_process_id, render_view_id);
   if (!web_contents)
     return false;
 
-  CaptureDeviceTabs::const_iterator iter = std::find_if(
-      tabs_.begin(), tabs_.end(), TabEquals(web_contents,
-                                            render_process_id,
-                                            render_view_id));
-  if (iter == tabs_.end())
-    return false;
-  return (iter->audio_ref_count > 0 || iter->video_ref_count > 0);
+  UsageMap::const_iterator it = usage_map_.find(web_contents);
+  return (it != usage_map_.end() &&
+          (it->second->IsCapturingAudio() || it->second->IsCapturingVideo()));
 }
 
-bool MediaStreamCaptureIndicator::IsProcessCapturingTab(
+bool MediaStreamCaptureIndicator::IsSupplyingMirroredMedia(
     int render_process_id, int render_view_id) const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  WebContents* web_contents = tab_util::GetWebContentsByID(render_process_id,
-                                                           render_view_id);
+
+  WebContents* const web_contents =
+      LookUpByKnownAlias(render_process_id, render_view_id);
   if (!web_contents)
     return false;
 
-  CaptureDeviceTabs::const_iterator iter = std::find_if(
-      tabs_.begin(), tabs_.end(), TabEquals(web_contents,
-                                            render_process_id,
-                                            render_view_id));
-  if (iter == tabs_.end())
-    return false;
-  return (iter->tab_capture_ref_count > 0);
+  UsageMap::const_iterator it = usage_map_.find(web_contents);
+  return it != usage_map_.end() && it->second->IsMirroring();
 }