media: Reenable Widevine EncryptedMediaTest on ChromeOS

Bug: 542697
Test: Reenable tests on ChromeOS
Change-Id: I8aaf97da6af5658760405c64b130f48f2dd0386a
Reviewed-on: https://chromium-review.googlesource.com/1087950Reviewed-by: John Rummell <jrummell@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565484}

chrome/browser/media/encrypted_media_browsertest.cc

@@ -541,12 +541,10 @@ INSTANTIATE_TEST_CASE_P(SRC_ClearKey,
 #endif  // BUILDFLAG(ENABLE_LIBRARY_CDMS)
 
 #if defined(WIDEVINE_CDM_AVAILABLE)
-#if !defined(OS_CHROMEOS)
 INSTANTIATE_TEST_CASE_P(MSE_Widevine,
                         EncryptedMediaTest,
                         Combine(Values(kWidevineKeySystem),
                                 Values(SrcType::MSE)));
-#endif  // !defined(OS_CHROMEOS)
 #endif  // defined(WIDEVINE_CDM_AVAILABLE)
 
 IN_PROC_BROWSER_TEST_P(EncryptedMediaTest, Playback_AudioClearVideo_WebM) {