Move GL headers from gpu to third_party/khronos

content/DEPS

 # Do NOT add chrome to the list below.  We shouldn't be including files from
 # src/chrome in src/content.
 include_rules = [
   "+crypto",
 
   "-chrome",
   # Until we move most of our testing infrastructure in a way that content can
   # make use of it.
   "+chrome/test",
 
@@ skipping 19 matching lines @@
   # Don't allow inclusion of these other libs we shouldn't be calling directly.
   "-v8",
   "-tools",
 
   # Allow inclusion of third-party code:
   "+third_party/gpsd",
   "+third_party/mozilla",
   "+third_party/npapi/bindings",
   "+third_party/sqlite",
   "+third_party/tcmalloc",
+  "+third_party/khronos",
   # Allow inclusion of WebKit API files.
   "+third_party/WebKit/Source/WebKit/chromium",
 
   # Aura is analogous to Win32 or a Gtk, so it is allowed.
   "+ui/aura",
   "+ui/base",
   "+ui/gfx",
   # Content knows about grd files, but the specifics of how to get a resource
   # given its id is left to the embedder.
   "-ui/base/l10n",
   "-ui/base/resource",
   # This file isn't related to grd, so it's fine.
   "+ui/base/l10n/l10n_util_win.h",
 
   # Content shouldn't depend on views. While we technically don't need this
   # line, since the top level DEPS doesn't allow it, we add it to make this
   # explicit. 
   "-views",
   
   # Aura Shell consumes views, so it too is banned.
   "-ui/aura_shell",
 
   "+webkit",
 ]