(This is a merge of go/wvgerrit/22441)
The IV incrementation code in Widevine DRM Plugin includes complexity
for handling partial crypto blocks in "cens" mode, a situation that
cannot actually happen. This commit changes the code to no longer handle
this case specially.
Bug: 28696811
Test: No tests for this code path due to bug 28295739
Change-Id: I77f8434a9785bf028509387c06db217a5de2b91b
3847adb78e