add the 'webpreferences' attribute to webviews

docs/api/web-view-tag.md

@@ -194,6 +194,20 @@ value will fail with a DOM exception.
 
 If "on", the guest page will be allowed to open new windows.
 
+### `webpreferences`
+
+```html
+<webview src="https://github.com" webpreferences="allowDisplayingInsecureContent, javascript=no"></webview>
+```
+
+A list of strings which specifies the web preferences to be set on the webview, separated by `,`.
+The full list of supported preference strings can be found in [BrowserWindow](browser-window.md#new-browserwindowoptions)
+
+The string follows the same format as the features string in `window.open`.
+A name by itself is given a `true` boolean value.
+A preference can be set to another value by including an `=`, followed by the value.
+Special values `yes` and `1` are interpreted as true, while `no` and `0` are interpreted as false.  
+
 ### `blinkfeatures`
 
 ```html

lib/browser/guest-view-manager.js

@@ -184,6 +184,31 @@ const attachGuest = function (embedder, elementInstanceId, guestInstanceId, para
     disableBlinkFeatures: params.disableblinkfeatures
   }
 
+  // parse the 'webpreferences' attribute string, if set
+  // this uses the same parsing rules as window.open uses for its features
+  if (typeof params.webpreferences === 'string') {
+    // split the attribute's value by ','
+    let webpreferencesTokens = params.webpreferences.split(/,\s*/)
+    for (i = 0, len = webpreferencesTokens.length; i < len; i++) {
+      // expected form is either a name by itself (true boolean flag)
+      // or a key/value, in the form of 'name=value'
+      // split the tokens by '='
+      let pref = webpreferencesTokens[i]
+      let prefTokens = pref.split(/\s*=/)
+      name = prefTokens[0]
+      value = prefTokens[1]
+      if (!name) continue
+
+      // interpret the value as a boolean, if possible 
+      value = (value === 'yes' || value === '1') ? true : (value === 'no' || value === '0') ? false : value
+      if (value === undefined) {
+        // no value was specified, default it to true
+        value = true
+      }
+      webPreferences[name] = value
+    }
+  }
+
   if (params.preload) {
     webPreferences.preloadURL = params.preload
   }

lib/renderer/web-view/web-view-attributes.js

@@ -312,6 +312,13 @@ class DisableBlinkFeaturesAttribute extends WebViewAttribute {
   }
 }
 
+// Attribute that specifies the web preferences to be enabled.
+class WebPreferencesAttribute extends WebViewAttribute {
+  constructor (webViewImpl) {
+    super(webViewConstants.ATTRIBUTE_WEBPREFERENCES, webViewImpl)
+  }
+}
+
 // Sets up all of the webview attributes.
 WebViewImpl.prototype.setupWebViewAttributes = function () {
   this.attributes = {}
@@ -328,6 +335,7 @@ WebViewImpl.prototype.setupWebViewAttributes = function () {
   this.attributes[webViewConstants.ATTRIBUTE_BLINKFEATURES] = new BlinkFeaturesAttribute(this)
   this.attributes[webViewConstants.ATTRIBUTE_DISABLEBLINKFEATURES] = new DisableBlinkFeaturesAttribute(this)
   this.attributes[webViewConstants.ATTRIBUTE_GUESTINSTANCE] = new GuestInstanceAttribute(this)
+  this.attributes[webviewConstants.ATTRIBUTE_WEBPREFERENCES] = new WebPreferencesAttribute(this)
 
   const autosizeAttributes = [webViewConstants.ATTRIBUTE_MAXHEIGHT, webViewConstants.ATTRIBUTE_MAXWIDTH, webViewConstants.ATTRIBUTE_MINHEIGHT, webViewConstants.ATTRIBUTE_MINWIDTH]
   autosizeAttributes.forEach((attribute) => {

lib/renderer/web-view/web-view-constants.js

@@ -18,6 +18,7 @@ module.exports = {
   ATTRIBUTE_BLINKFEATURES: 'blinkfeatures',
   ATTRIBUTE_DISABLEBLINKFEATURES: 'disableblinkfeatures',
   ATTRIBUTE_GUESTINSTANCE: 'guestinstance',
+  ATTRIBUTE_WEBPREFERENCES: 'webpreferences',
 
   // Internal attribute.
   ATTRIBUTE_INTERNALINSTANCEID: 'internalinstanceid',