Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/tts_engine.json

Index: chrome/common/extensions/api/tts_engine.json
diff --git a/chrome/common/extensions/api/tts_engine.json b/chrome/common/extensions/api/tts_engine.json
index 4c6bb264dd533cf6b26a1d63c136209b07545ff4..285bb93ddef97192b423bc06bc166e04c09529e5 100644
--- a/chrome/common/extensions/api/tts_engine.json
+++ b/chrome/common/extensions/api/tts_engine.json
@@ -5,6 +5,7 @@
 [
   {
     "namespace": "ttsEngine",
+    "description": "Use the <code>chrome.ttsEngine</code> module to implement a text-to-speech(TTS) engine using an extension. If your extension registers using this API, it will receive events containing an utterance to be spoken and other parameters when any extension or packaged app uses the <a href='tts.html'>tts</a> module to generate speech. Your extension can then use any available web technology to synthesize and output the speech, and send events back to the calling function to report the status.",
     "functions": [
       {
         "name": "sendTtsEvent",