Moving the MHTML API out of experimental and renaming it.

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 9060 matching lines @@
             "type": "function",
             "description": "Called when the browser's passwords have been cleared.",
             "optional": true,
             "parameters": []
           }
         ]
       }
     ]
   },
   {
-    "namespace": "experimental.savePage",
+    "namespace": "pageCapture",
     "functions": [
       {
         "name": "saveAsMHTML",
         "type": "function",
         "description": "Saves the content of the tab with given id as MHTML.",
         "parameters": [
           {
             "name": "details",
             "type": "object",
             "properties": {
@@ skipping 52 matching lines @@
                   }
                 }
               }
             ]
           }
         ]
       }
     ]
   }
 ]