Add a JS API for detecting WebGL availability.

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "types": [
       {
         "id": "MessageSender",
         "type": "object",
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
           "tab": {"$ref": "Tab", "optional": true, "description":"This property will <b>only</b> be present when the connection was opened from a tab or content script."},
@@ skipping 8068 matching lines @@
                 "name": "info",
                 "type": "object",
                 "properties": {
                   "login": { "type": "string", "optional": true },
                   "token": { "type": "string", "optional": true }
                 }
               }
             ]
           }
         ]
+      },
+      {
+        "name": "getWebGLStatus",
+        "description": "Invokes a callback that returns whether WebGL is blacklisted or not.",
+        "parameters": [
+          {
+            "name": "callback",
+            "type": "function",
+            "optional": "false",
+            "parameters": [
+              {
+                "name": "webgl_status",
+                "type": "string",
+                "enum": ["webgl_allowed", "webgl_blocked"]
+              }
+            ]
+          }
+        ]
       }
     ]
   },
   {
     "namespace": "webSocketProxyPrivate",
     "nodoc": true,
     "types": [],
     "functions": [
       {
         "name": "getPassportForTCP",
@@ skipping 1248 matching lines @@
                   }
                 }
               }
             ]
           }
         ]
       }
     ]
   }
 ]