Revert "Don't trust the manifest's computed branch for revision locked manifests."
Revert "Don't trust the manifest's computed branch for revision locked manifests."

Reversion of CL:29389; not guranteed, but seems very, very likely to be implicated in 

https://uberchromegw.corp.google.com/i/chromeos/builders/tegra2%20kaen%20paladin/builds/7693/steps/CommitQueueSync/logs/stdio

This reverts commit fdc318b234e79ce95fa812bdd72411e3aa19e117

Change-Id: I9bc68482a278a362e1f9cc56ca93b136f781ede5
Reviewed-on: https://gerrit.chromium.org/gerrit/29561
Reviewed-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>
Tested-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>

zhang0137/chromite,zhang0137/chromite,coreos/chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,coreos/chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,zhang0137/chromite