Add code to support options for TTS speak.

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 497 matching lines @@
                 "optional": true,
                 "description": "The language name for synthesis specified in the form <language>-<locale>, e.g. en-US, en-GB, fr-CA, zh-CN, etc."
               },
               "gender": {
                 "type": "string",
                 "optional": true,
                 "description": "Gender of voice for synthesized speech.",
                 "enum": ["male", "female"]
               },
               "rate": {
-                "type": "float",
+                "type": "number",
                 "optional": true,
                 "minimum": 0,
                 "maximum": 1,
                 "description": "Speaking speed between 0 and 1 inclusive, with 0 being slowest and 1 being fastest."
               },
               "pitch": {
-                "type": "float",
+                "type": "number",
                 "optional": true,
                 "minimum": 0,
                 "maximum": 1,
                 "description": "Speaking pitch between 0 and 1 inclusive, with 0 being lowest and 1 being highest."
               },
               "volume": {
-                "type": "float",
+                "type": "number",
                 "optional": true,
                 "minimum": 0,
                 "maximum": 1,
                 "description": "Speaking volume between 0 and 1 inclusive, with 0 being lowest and 1 being highest."
               }
             }
           },
           {
             "type": "function",
             "name": "callback",
@@ skipping 3298 matching lines @@
       {
         "name": "onInputCancelled",
         "perExtensionEvent": true,
         "type": "function",
         "description": "User has ended the keyword input session without accepting the input.",
         "parameters": []
       }
     ]
   }
 ]