Fix plugin grouping for PDF in about:plugins

chrome/browser/resources/plugin_metadata/plugins_mac.json

 {
   "x-version": 8,
   "google-talk": {
     "mime_types": [
     ],
     "versions": [
       {
         "version": "0",
         "status": "requires_authorization",
         "comment": "'Google Talk Plugin' and 'Google Talk Plugin Video Accelerator' use two completely different versioning schemes, so we can't define a minimum version."
@@ skipping 266 matching lines @@
     "versions": [
       {
         "version": "0",
         "status": "up_to_date",
         "comment": "Chrome PDF Viewer has no version information."
       }
     ],
     "name": "Chrome PDF Viewer",
     "group_name_matcher": "*Chrome PDF Viewer*"
   },
+  "chromium-pdf": {
+    "mime_types": [
+    ],
+    "versions": [
+      {
+        "version": "0",
+        "status": "up_to_date",
+        "comment": "Chrome PDF Viewer has no version information."
+      }
+    ],
+    "name": "Chromium PDF Viewer",
+    "group_name_matcher": "*Chromium PDF Viewer*"
+  },
   "facebook-video-calling": {
     "mime_types": [
       "application/skypesdk-plugin"
     ],
     "versions": [
       {
         "version": "0",
         "status": "requires_authorization",
         "comment": "We do not track version information for the Facebook Video Calling Plugin."
       }
@@ skipping 13 matching lines @@
         "status": "requires_authorization",
         "comment": "We do not track version information for the Google Earth Plugin."
       }
     ],
     "lang": "en-US",
     "name": "Google Earth",
     "url": "http://www.google.com/earth/explore/products/plugin.html",
     "group_name_matcher": "*Google Earth*"
   }
 }