Re-land webrtcmediaengine.cc part of r6397.
Re-land webrtcmediaengine.cc part of r6397.

webrtcvideoengine.cc un-reverted by a bot roll in r6399 so half of r6397
is still applied. The applied fix (diff between r6397) is to put
WebRtcVideoEngine2 in ifdefs and only build for WEBRTC_CHROMIUM_BUILDs
corresponding to webrtcmediaengine.h.

BUG=
R=minyue@webrtc.org
TBR=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/19719005

git-svn-id: a556c8bde68cedbc0208a1ffc78b06e9cd07f676@6401 4adac7df-926f-26a2-2b94-8c16560cd09d

xin3liang/platform_external_chromium_org_third_party_libjingle_source_talk,AOSPU/external_chromium_org_third_party_libjingle_source_talk,bpsinc-native/src_third_party_libjingle_source_talk,sippet/talk,xin3liang/platform_external_chromium_org_third_party_libjingle_source_talk,xin3liang/platform_external_chromium_org_third_party_libjingle_source_talk,AOSPU/external_chromium_org_third_party_libjingle_source_talk,dcpang/fatline-libjingle,android-ia/platform_external_chromium_org_third_party_libjingle_source_talk,Omegaphora/external_chromium_org_third_party_libjingle_source_talk,Omegaphora/external_chromium_org_third_party_libjingle_source_talk,Omegaphora/external_chromium_org_third_party_libjingle_source_talk,geekboxzone/lollipop_external_chromium_org_third_party_libjingle_source_talk,sippet/talk,geekboxzone/lollipop_external_chromium_org_third_party_libjingle_source_talk,AOSPU/external_chromium_org_third_party_libjingle_source_talk,android-ia/platform_external_chromium_org_third_party_libjingle_source_talk,Omegaphora/external_chromium_org_third_party_libjingle_source_talk,android-ia/platform_external_chromium_org_third_party_libjingle_source_talk,Omegaphora/external_chromium_org_third_party_libjingle_source_talk,AOSPU/external_chromium_org_third_party_libjingle_source_talk,android-ia/platform_external_chromium_org_third_party_libjingle_source_talk,bpsinc-native/src_third_party_libjingle_source_talk,geekboxzone/lollipop_external_chromium_org_third_party_libjingle_source_talk,geekboxzone/lollipop_external_chromium_org_third_party_libjingle_source_talk,dcpang/fatline-libjingle,xin3liang/platform_external_chromium_org_third_party_libjingle_source_talk,xin3liang/platform_external_chromium_org_third_party_libjingle_source_talk,AOSPU/external_chromium_org_third_party_libjingle_source_talk,bpsinc-native/src_third_party_libjingle_source_talk,bpsinc-native/src_third_party_libjingle_source_talk,Omegaphora/external_chromium_org_third_party_libjingle_source_talk,bpsinc-native/src_third_party_libjingle_source_talk,bpsinc-native/src_third_party_libjingle_source_talk,dcpang/fatline-libjingle,android-ia/platform_external_chromium_org_third_party_libjingle_source_talk,dcpang/fatline-libjingle,sippet/talk,geekboxzone/lollipop_external_chromium_org_third_party_libjingle_source_talk,sippet/talk,dcpang/fatline-libjingle,sippet/talk,android-ia/platform_external_chromium_org_third_party_libjingle_source_talk