Add docs for chrome.wallpaper API

chrome/common/extensions/api/wallpaper.json

Index: chrome/common/extensions/api/wallpaper.json
diff --git a/chrome/common/extensions/api/wallpaper.json b/chrome/common/extensions/api/wallpaper.json
index 59f7cb5be4765d5761d94a869ed795b610419783..70baecce8a22e8fd4799a341d1a2192fcd65c617 100644
--- a/chrome/common/extensions/api/wallpaper.json
+++ b/chrome/common/extensions/api/wallpaper.json
@@ -9,13 +9,12 @@
       "implemented_in": "chrome/browser/chromeos/extensions/wallpaper_api.h"
     },
     "platforms": ["chromeos"],
-    "description": "none",
+    "description": "Use the <code>chrome.wallpaper</code> API to change the ChromeOS wallpaper.",
     "functions": [
     {
       "name": "setWallpaper",
       "type": "function",
-      "description": "Sets wallpaper to the image from url with specified layout",
-      "nodoc": "true",
+      "description": "Sets wallpaper to the image at <code>url</code> or <code>wallpaperData</code> with the specified layout",
       "parameters": [
         {
           "name": "details",
@@ -29,7 +28,7 @@
             "url": {
               "type": "string",
               "optional": true,
-              "description": "The url of online wallpaper."
+              "description": "The URL of the wallpaper to be set. If host permissions for this URL are not specified in the manifest file, the API call will fail."
             },
             "layout": {
               "type": "string",
@@ -38,7 +37,7 @@
             },
             "name": {
               "type": "string",
-              "description": "The file name of saved wallpaper."
+              "description": "The file name of the saved wallpaper."
             },
             "thumbnail": {
               "type": "boolean",
@@ -54,7 +53,8 @@
             {
               "type": "binary",
               "optional": true,
-              "name": "thumbnail"
+              "name": "thumbnail",
+              "description": "The jpeg encoded wallpaper thumbnail. It is generated by resizing the wallpaper to 128x60."
             }
           ]
         }