Revert 174811

Revert 174811
> Allow NPAPI & Trusted Broker plugins access to OS-level HighDPI APIs.
> 
> As per crrev.com/10069029, OS 10.7.3 and above report low-DPI to
> processes that lack an NSPrincipalClass key in their manifest.  Because
> Chromium Helper processes lacked this key, NPAPI or Trusted Broker
> plugins they hosted could not use the OS HighDPI APIs.
> 
> This CL adds the key to Chromium's Helper process plist, so that APIs
> such as -[NSScreen backingScaleFactor] will now return 2 under HighDPI.
> 
> Note that NPAPI plugins still can't paint HighDPI surfaces yet because
> chrome doesn't implement the NPAPI ContentsScaleFactor specification
> (see crbug.com/31960).
> 
> BUG=167209
> 
> Review URL: https://chromiumcodereview.appspot.com/11642052

Making NPAPI host processes DPI-aware appears to break Netflix' Silverlight
client when it is running full-screen.

BUG=167209, 172559
TBR=wez@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=180015