Update TTS extension API docs to reflect latest changes. Note that this

chrome/common/extensions/api/extension_api.json

Index: chrome/common/extensions/api/extension_api.json
===================================================================
--- chrome/common/extensions/api/extension_api.json	(revision 92678)
+++ chrome/common/extensions/api/extension_api.json	(working copy)
@@ -517,7 +517,7 @@
           "type": {
             "type": "string",
             "enum": ["start", "end", "word", "sentence", "marker", "interrupted", "cancelled", "error"],
-            "description": "The message can be 'start' when this utterance is begun to be spoken, '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, and 'error' when any other error occurs. Clients will always receive 'end', 'cancelled', 'interrupted', or 'error', and other events will depend on the engine."
+            "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."
           },
           "charIndex": {
             "type": "number",
@@ -526,7 +526,7 @@
           },
           "errorMessage": {
             "type": "string",
-            "description": "The error message, if the message is 'error'.",
+            "description": "The error description, if the event type is 'error'.",
             "optional": true
           },
           "srcId": {
@@ -556,7 +556,7 @@
           "lang": {
             "type": "string",
             "optional": true,
-            "description": "The language that this voice supports, in the form <language>-<region>. Examples: 'en', 'en-US', 'en-GB', 'zh-CN', etc."
+            "description": "The language that this voice supports, in the form <em>language</em>-<em>region</em>. Examples: 'en', 'en-US', 'en-GB', 'zh-CN'."
           },
           "gender": {
             "type": "string",
@@ -587,7 +587,7 @@
           {
             "type": "string",
             "name": "utterance",
-            "description": "The text to speak, either plaintext or a complete well-formed SSML document. Speech engines that do not support SSML will strip away the tags and speak the text. The maximum length of the text is 32,768 characters."
+            "description": "The text to speak, either plain text or a complete, well-formed SSML document. Speech engines that do not support SSML will strip away the tags and speak the text. The maximum length of the text is 32,768 characters."
           },
           {
             "type": "object",
@@ -608,12 +608,12 @@
 	      "extensionId": {
                 "type": "string",
                 "optional": true,
-                "description": "The specific extension ID of the speech engine to use, if known."
+                "description": "The extension ID of the speech engine to use, if known."
               },
 	      "lang": {
                 "type": "string",
                 "optional": true,
-                "description": "The language to be used for synthesis, in the form &lt;language&gt;-&lt;region&gt;. Examples: 'en', 'en-US', 'en-GB', 'zh-CN', etc."
+                "description": "The language to be used for synthesis, in the form <em>language</em>-<em>region</em>. Examples: 'en', 'en-US', 'en-GB', 'zh-CN'."
               },
               "gender": {
                 "type": "string",
@@ -626,14 +626,14 @@
                 "optional": true,
                 "minimum": 0.1,
                 "maximum": 10,
-                "description": "Speaking rate relative to the default rate for this voice. 1.0 is the default rate, normally around 180 to 220 words per minute, 2.0 would be twice as fast, and 0.5 would be half as fast. Values below 0.1 or above 10.0 are strictly disallowed, but many voices will constrain the minimum and maximum rates further - i.e. a particular voice may not actually speak faster than 3 times normal even if you specify a value larger than 3.0."
+                "description": "Speaking rate relative to the default rate for this voice. 1.0 is the default rate, normally around 180 to 220 words per minute. 2.0 is twice as fast, and 0.5 is half as fast. Values below 0.1 or above 10.0 are strictly disallowed, but many voices will constrain the minimum and maximum rates further&mdash;for example a particular voice may not actually speak faster than 3 times normal even if you specify a value larger than 3.0."
               },
               "pitch": {
                 "type": "number",
                 "optional": true,
                 "minimum": 0,
                 "maximum": 2,
-                "description": "Speaking pitch between 0 and 2 inclusive, with 0 being lowest and 1 being highest, with 1.0 being the default pitch of this particular voice."
+                "description": "Speaking pitch between 0 and 2 inclusive, with 0 being lowest and 2 being highest. 1.0 corresponds to a voice's default pitch."
               },
               "volume": {
                 "type": "number",
@@ -646,15 +646,15 @@
                 "type": "array",
                 "items": {"type": "string"},
                 "optional": true,
-                "description": "The TTS event types the voice must support. If missing, this criteria will not be used to filter voices."
+                "description": "The TTS event types the voice must support."
               },
               "desiredEventTypes": {
                 "type": "array",
                 "items": {"type": "string"},
                 "optional": true,
-                "description": "The TTS event types that should be sent. If missing, all event types will be sent."
+                "description": "The TTS event types that you are interested in listening to. If missing, all event types may be sent."
               },
-              "onevent": {
+              "onEvent": {
                 "type": "function",
                 "optional": true,
                 "description": "This function is called with events that occur in the process of speaking the utterance.",
@@ -672,7 +672,7 @@
             "type": "function",
             "name": "callback",
             "optional": true,
-            "description": "Called right away, before speech finishes. Check chrome.extension.lastError to make sure there were no errors. Use options.onevent to get more detailed feedback.",
+            "description": "Called right away, before speech finishes. Check chrome.extension.lastError to make sure there were no errors. Use options.onEvent to get more detailed feedback.",
             "parameters": []
           }
         ]
@@ -749,17 +749,17 @@
       {
         "name": "onSpeak",
         "type": "function",
-        "description": "Called when the user makes a call to tts.speak and the options matches one of the tts_voices from this extension's manifest.",
+        "description": "Called when the user makes a call to tts.speak() and one of the voices from this extension's manifest is the first to match the options object.",
         "parameters": [
           {
             "type": "string",
             "name": "utterance",
-            "description": "The text to speak. This may include SSML, so if your engine does not support SSML, you should strip out all XML markup and synthesize only the underlying text content. This is guaranteed to be no more than 32,768 characters. If this engine does not support speaking that many characters at a time, the utterance should be split into smaller chunks and queued internally without returning an error."
+            "description": "The text to speak, specified as either plain text or an SSML document. If your engine does not support SSML, you should strip out all XML markup and synthesize only the underlying text content. The value of this parameter is guaranteed to be no more than 32,768 characters. If this engine does not support speaking that many characters at a time, the utterance should be split into smaller chunks and queued internally without returning an error."
           },
           {
             "type": "object",
             "name": "options",
-            "description": "The speak options.",
+            "description": "Options specified to the tts.speak() method.",
             "properties": {
 	      "voiceName": {
                 "type": "string",
@@ -769,7 +769,7 @@
 	      "lang": {
                 "type": "string",
                 "optional": true,
-                "description": "The language to be used for synthesis, in the form <language>-<region>, e.g. en-US, en-GB, fr-CA, zh-CN, etc."
+                "description": "The language to be used for synthesis, in the form <em>language</em>-<em>region</em>. Examples: 'en', 'en-US', 'en-GB', 'zh-CN'."
               },
               "gender": {
                 "type": "string",
@@ -782,14 +782,14 @@
                 "optional": true,
                 "minimum": 0.1,
                 "maximum": 10.0,
-                "description": "Speaking rate relative to the default rate for this voice. 1.0 is the default rate, normally around 180 to 220 words per minute, 2.0 would be twice as fast, and 0.5 would be half as fast.  This value is guaranteed to be between 0.1 and 10.0, inclusive. When a voice does not support this full range of rates, the actual rate should be clipped to the range that is supported without returning an error."
+                "description": "Speaking rate relative to the default rate for this voice. 1.0 is the default rate, normally around 180 to 220 words per minute. 2.0 is twice as fast, and 0.5 is half as fast. This value is guaranteed to be between 0.1 and 10.0, inclusive. When a voice does not support this full range of rates, don't return an error. Instead, clip the rate to the range the voice supports."
               },
               "pitch": {
                 "type": "number",
                 "optional": true,
                 "minimum": 0,
                 "maximum": 2,
-                "description": "Speaking pitch between 0 and 2 inclusive, with 0 being lowest and 1 being highest, with 1.0 being the default pitch of this particular voice."
+                "description": "Speaking pitch between 0 and 2 inclusive, with 0 being lowest and 2 being highest. 1.0 corresponds to this voice's default pitch."
               },
               "volume": {
                 "type": "number",