Fix webview tag's documentation to specify correct ClearDataTypeSet for clearData API.

BUG=371488
NOTRY=true
Test=The preview link for this patch is:
https://chrome-apps-doc.appspot.com/_patch/271913003/apps/tags/webview#type-ClearDataTypeSet

Once the change is committed, this can be viewed in 
https://developer.chrome.com/apps/tags/webview#type-ClearDataTypeSet

You should see only 6 items listed as types:
appcache/cookies/fileSystems/indexedDB/localStorage/webSQL
And it should not list unsupported items such as "downloads", "pluginData", ... which it does without this change.

Review URL: https://codereview.chromium.org/271913003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269440 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/api/webview_tag.json

@@ -30,17 +30,10 @@
         "description": "A set of data types. Missing properties are interpreted as <code>false</code>.",
         "properties": {
           "appcache": { "type": "boolean", "optional": true, "description": "Websites' appcaches." },
-          "cache": { "type": "boolean", "optional": true, "description": "The partition's cache. Note: This clears the entire cache regardless of the age passed to <code>clearData</code>." },
           "cookies": { "type": "boolean", "optional": true, "description": "The partition's cookies." },
-          "downloads": { "type": "boolean", "optional": true, "description": "The partition's download list." },
           "fileSystems": { "type": "boolean", "optional": true, "description": "Websites' filesystems." },
-          "formData": { "type": "boolean", "optional": true, "description": "The partition's stored form data." },
-          "history": { "type": "boolean", "optional": true, "description": "The partition's history." },
           "indexedDB": { "type": "boolean", "optional": true, "description": "Websites' IndexedDB data." },
           "localStorage": { "type": "boolean", "optional": true, "description": "Websites' local storage data." },
-          "serverBoundCertificates": { "type": "boolean", "optional": true, "description": "Server-bound certificates." },
-          "pluginData": { "type": "boolean", "optional": true, "description": "Plugins' data." },
-          "passwords": { "type": "boolean", "optional": true, "description": "Stored passwords." },
           "webSQL": { "type": "boolean", "optional": true, "description": "Websites' WebSQL data." }
         }
       },