Fix crash in reading audio capture device name.

Relevant crash report: http://crash/reportdetail?reportid=c48906f8d604a9d5#crashing_thread

BUG=69608
TEST=none

Review URL: http://codereview.chromium.org/6333005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71434 0039d316-1c4b-4281-b951-d872f2087c98

media/audio/win/audio_manager_win.cc

@@ -177,6 +177,9 @@ string16 AudioManagerWin::GetAudioInputDeviceModel() {
   waveInMessage(reinterpret_cast<HWAVEIN>(device_id),
                 DRV_QUERYDEVICEINTERFACESIZE,
                 reinterpret_cast<DWORD_PTR>(&device_interface_name_size), 0);
+  if (device_interface_name_size == 0)  // No audio capture device?
+    return string16();
+
   string16 device_interface_name;
   string16::value_type* name_ptr = WriteInto(&device_interface_name,
       device_interface_name_size / sizeof(string16::value_type));