MediaStreamCaptureIndicator: fix crash due to destruction on wrong thread

chrome/browser/media/media_stream_capture_indicator.cc

Index: chrome/browser/media/media_stream_capture_indicator.cc
diff --git a/chrome/browser/media/media_stream_capture_indicator.cc b/chrome/browser/media/media_stream_capture_indicator.cc
index 68d56432d159b180f53138cd8b54fd3233c8925e..e937ceefa3cfca4626ae03557112d7400914ac8c 100644
--- a/chrome/browser/media/media_stream_capture_indicator.cc
+++ b/chrome/browser/media/media_stream_capture_indicator.cc
@@ -122,7 +122,6 @@ MediaStreamCaptureIndicator::MediaStreamCaptureIndicator()
       mic_image_(NULL),
       camera_image_(NULL),
       balloon_image_(NULL),
-      ALLOW_THIS_IN_INITIALIZER_LIST(tracker_(this)),
       request_index_(0) {
 }
 
@@ -275,7 +274,8 @@ void MediaStreamCaptureIndicator::ShowBalloon(
     pending_messages_[request_index_++] =
         l10n_util::GetStringFUTF16(message_id,
                                    UTF8ToUTF16(extension->name()));
-    tracker_.LoadImage(
+    EnsureImageLoadingTracker();
+    tracker_->LoadImage(
         extension,
         extension->GetIconResource(32, ExtensionIconSet::MATCH_BIGGER),
         gfx::Size(32, 32),
@@ -307,6 +307,10 @@ void MediaStreamCaptureIndicator::OnImageLoaded(
 
 void MediaStreamCaptureIndicator::Hide() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  // We have to destroy |tracker_| on the UI thread.
+  tracker_.reset();
+
   if (!status_icon_)
     return;
 
@@ -445,3 +449,12 @@ void MediaStreamCaptureIndicator::RemoveCaptureDeviceTab(
     UpdateStatusTrayIconContextMenu();
 }
 
+void MediaStreamCaptureIndicator::EnsureImageLoadingTracker() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  if (tracker_.get())
+    return;
+
+  tracker_.reset(new ImageLoadingTracker(this));
+  pending_messages_.clear();
+  request_index_ = 0;
+}