Pull latest PPAPI to make completion callback compile

TEST=none
BUG=none
Review URL: http://codereview.chromium.org/2852021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@50936 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -155,7 +155,7 @@ deps = {
     Var("libvpx_revision"),
 
   "src/third_party/ppapi":
-    "http://ppapi.googlecode.com/svn/trunk@77",
+    "http://ppapi.googlecode.com/svn/trunk@79",
 
   "src/third_party/libjingle/source":
     "http://libjingle.googlecode.com/svn/branches/nextsnap@" +