fix comparison of StreamDeviceInfoArray.

Need check size of both arrays before calling std::equal.

BUG=141904
Review URL: https://chromiumcodereview.appspot.com/10854099

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151140 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/media/media_stream_manager.cc

@@ -546,6 +546,7 @@ void MediaStreamManager::DevicesEnumerated(
        &audio_enumeration_cache_ : &video_enumeration_cache_);
   if (HasEnumerationRequest(stream_type) &&
       (!cache->valid ||
+       devices.size() != cache->devices.size() ||
        !std::equal(devices.begin(), devices.end(), cache->devices.begin(),
                    media_stream::StreamDeviceInfo::IsEqual))) {
     cache->valid = true;