AC3 EAC3 checks are also missed.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f5ff9e38f2a20950f26f7afe79b175328ce5700d

commit f5ff9e38f2a20950f26f7afe79b175328ce5700d
Author: yucliu <yucliu@chromium.org>
Date: Wed Apr 26 20:16:54 2017

EME contentType checks DolbyVision

Add new enum to EmeCodec:
EME_CODEC_MP4_DV_AVC
EME_CODEC_MP4_DV_HEVC

BUG= 710167 
TEST=requestMediaKeySystemAccess with dv codec on cast

Review-Url: https://codereview.chromium.org/2809013002
Cr-Commit-Position: refs/heads/master@{#467431}

[modify] https://crrev.com/f5ff9e38f2a20950f26f7afe79b175328ce5700d/chromecast/renderer/media/key_systems_cast.cc
[modify] https://crrev.com/f5ff9e38f2a20950f26f7afe79b175328ce5700d/components/cdm/browser/cdm_message_filter_android.cc
[modify] https://crrev.com/f5ff9e38f2a20950f26f7afe79b175328ce5700d/media/base/eme_constants.h
[modify] https://crrev.com/f5ff9e38f2a20950f26f7afe79b175328ce5700d/media/base/key_systems.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7d30cf67b1bd1b78cc95ef9ad88f421bc9bc01f4

commit 7d30cf67b1bd1b78cc95ef9ad88f421bc9bc01f4
Author: yucliu <yucliu@chromium.org>
Date: Tue May 02 18:44:27 2017

EME contentType checks for AC3/EAC3

Add missed EME contentType checks for 'ac-3', 'ec-3'

Bug:  710167 
Test: Test on Cast, Cast for Android
Review-Url: https://codereview.chromium.org/2853123003
Cr-Commit-Position: refs/heads/master@{#468715}

[modify] https://crrev.com/7d30cf67b1bd1b78cc95ef9ad88f421bc9bc01f4/chromecast/renderer/media/key_systems_cast.cc
[modify] https://crrev.com/7d30cf67b1bd1b78cc95ef9ad88f421bc9bc01f4/components/cdm/browser/cdm_message_filter_android.cc
[modify] https://crrev.com/7d30cf67b1bd1b78cc95ef9ad88f421bc9bc01f4/media/base/eme_constants.h
[modify] https://crrev.com/7d30cf67b1bd1b78cc95ef9ad88f421bc9bc01f4/media/base/key_systems.cc
[modify] https://crrev.com/7d30cf67b1bd1b78cc95ef9ad88f421bc9bc01f4/media/base/key_systems_unittest.cc