Move the tts and ttsEngine APIs out of experimental, and give

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "unprivileged": true,
     "types": [
       {
         "id": "MessageSender",
         "type": "object",
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
@@ skipping 489 matching lines @@
           {
             "$ref": "AccessibilityObject",
             "name": "menu",
             "description": "Information about the menu that was closed."
           }
         ]
       }
     ]
   },
   {
-    "namespace": "experimental.tts",
+    "namespace": "tts",
     "types": [
       {
         "id": "TtsEvent",
         "type": "object",
         "description": "An event from the TTS engine to communicate the status of an utterance.",
         "properties": {
           "type": {
             "type": "string",
             "enum": ["start", "end", "word", "sentence", "marker", "interrupted", "cancelled", "error"],
             "description": "The type can be 'start' as soon as speech has started, 'word' when a word boundary is reached, 'sentence' when a sentence boundary is reached, 'marker' when an SSML mark element is reached, 'end' when the end of the utterance is reached, 'interrupted' when the utterance is stopped or interrupted before reaching the end, 'cancelled' when it's removed from the queue before ever being synthesized, or 'error' when any other error occurs."
@@ skipping 194 matching lines @@
               {
                 "type": "array",
                 "name": "voices",
                 "items": { "$ref": "TtsVoice" },
                 "description": "Array of $ref:TtsVoice objects representing the available voices for speech synthesis."
               }
             ]
           }
         ]
       }
+    ],
+    "events": [
+      {
+        "name": "onEvent",
+        "type": "function",
+        "nodoc": true,
+        "parameters": [
+          {
+            "name": "event",
+            "$ref": "TtsEvent",
+            "description": "The event from the text-to-speech engine indicating the status of this utterance."
+          }
+        ],
+        "description": "Used to pass events back to the function calling speak()."
+      }
     ]
   },
   {
-    "namespace": "experimental.ttsEngine",
+    "namespace": "ttsEngine",
     "functions": [
       {
         "name": "sendTtsEvent",
         "nodoc": true,
         "type": "function",
         "description": "Route a TTS event from a speech engine to a client.",
         "parameters": [
           {
             "type": "integer",
             "name": "requestId"
@@ skipping 72 matching lines @@
                 "description": "The event from the text-to-speech engine indicating the status of this utterance."
               }
             ]
           }
         ]
       },
       {
         "name": "onStop",
         "type": "function",
         "description": "Fired when a call is made to tts.stop and this extension may be in the middle of speaking. If an extension receives a call to onStop and speech is already stopped, it should do nothing (not raise an error)."
-      },
-      {
-        "name": "onEvent",
-        "type": "function",
-        "nodoc": true,
-        "parameters": [
-          {
-            "name": "event",
-            "$ref": "TtsEvent",
-            "description": "The event from the text-to-speech engine indicating the status of this utterance."
-          }
-        ],
-        "description": "Used to pass events back to the function calling speak()."
       }
     ]
   },
   {
     "namespace": "windows",
     "types": [
       {
         "id": "Window",
         "type": "object",
         "properties": {
@@ skipping 5653 matching lines @@
                 "description": "A string result code. The value is non-empty on success only in tests.",
                 "optional": "true"
               }
             ]
           }
         ]
       }
     ]
   }
 ]