Add code to support options for TTS speak.

chrome/common/extensions/api/extension_api.json

Index: chrome/common/extensions/api/extension_api.json
===================================================================
--- chrome/common/extensions/api/extension_api.json	(revision 56764)
+++ chrome/common/extensions/api/extension_api.json	(working copy)
@@ -515,21 +515,21 @@
                 "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,