Prevent conflicts between WebViews settings

When we want to stop javaScript, switch to another WebPreferences instead
of modifying the current one.
Because WebPreferences can be shared among multiple WebView, as described by
https://developer.apple.com/documentation/webkit/webpreferences?language=objc,
modifying javaScriptEnabled for a single WebView could affect others.

src/BrowserPane.m

@@ -694,8 +694,8 @@ -(IBAction)handleReload:(id)sender
 -(void)handleStopLoading:(id)sender
 {
 	[self willChangeValueForKey:@"isLoading"];
-	[self.webPane.preferences setPlugInsEnabled:NO];
-	[self.webPane.preferences setJavaScriptEnabled:NO];
+	// stop Javascript and plugings
+	[self.webPane abortJavascriptAndPlugIns];
 	[self.webPane setFrameLoadDelegate:nil];
 	[self.webPane setUIDelegate:nil];
 	[self.webPane stopLoading:self];

src/TabbedWebView.h

@@ -24,7 +24,6 @@
 @class AppController;
 
 @interface TabbedWebView : WebView <WebPolicyDelegate> {
-	WebPreferences * defaultWebPrefs;
 	BOOL openLinksInNewBrowser;
 	BOOL isFeedRedirect;
 	BOOL isDownload;
@@ -36,6 +35,7 @@
 -(void)setOpenLinksInNewBrowser:(BOOL)flag;
 -(void)keyDown:(NSEvent *)theEvent;
 -(void)printDocument:(id)sender;
+-(void)abortJavascriptAndPlugIns;
 @property (nonatomic, getter=isFeedRedirect, readonly) BOOL feedRedirect;
 @property (nonatomic, getter=isDownload, readonly) BOOL download;
 -(void)scrollToTop;

src/TabbedWebView.m

@@ -85,6 +85,37 @@ +(NSArray *)downloadableExtensions
     return @[@"dmg",  @"zip", @"gz", @"tgz", @"7z", @"rar", @"tar", @"bin", @"bz2", @"exe", @"sit", @"sitx"];
 }
 
++(WebPreferences *)defaultWebPrefs
+{
+    // Singleton
+    static WebPreferences * _webPrefs = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        _webPrefs = [[WebPreferences alloc] initWithIdentifier:@"VNAStandardWebPrefs"];
+        _webPrefs.standardFontFamily = @"Arial";
+        _webPrefs.defaultFontSize = 12;
+        _webPrefs.privateBrowsingEnabled = NO;
+    });
+    return _webPrefs;
+}
+
++(WebPreferences *)passiveWebPrefs
+{
+    // Singleton
+    static WebPreferences * _webPrefs = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        _webPrefs = [[WebPreferences alloc] initWithIdentifier:@"VNAPassiveWebPrefs"];
+        _webPrefs.standardFontFamily = @"Arial";
+        _webPrefs.defaultFontSize = 12;
+        _webPrefs.privateBrowsingEnabled = NO;
+        _webPrefs.javaScriptEnabled = NO;
+        _webPrefs.plugInsEnabled = NO;
+    });
+    return _webPrefs;
+}
+
+
 /* initWithFrame
  * The designated instance initialiser.
  */
@@ -121,15 +152,10 @@ -(void)initTabbedWebView
     [nc addObserver:self selector:@selector(handleUseWebPluginsChange:)
                name:kMA_Notify_UseWebPluginsChange object:nil];
 
-	// Handle minimum font size, use of JavaScript, and use of plugins
-	defaultWebPrefs = self.preferences;
-	defaultWebPrefs.standardFontFamily = @"Arial";
-	defaultWebPrefs.defaultFontSize = 12;
-	[defaultWebPrefs setPrivateBrowsingEnabled:NO];
-	[defaultWebPrefs setJavaScriptEnabled:NO];
-    [defaultWebPrefs setPlugInsEnabled:NO];
     // handle UserAgent
     self.customUserAgent = [TabbedWebView userAgent];
+	// Handle minimum font size, use of JavaScript, and use of plugins
+	self.preferences = [TabbedWebView defaultWebPrefs];
 	[self loadMinimumFontSize];
 	[self loadUseJavaScript];
     [self loadUseWebPlugins];
@@ -336,11 +362,11 @@ -(void)loadMinimumFontSize
 {
 	Preferences * prefs = [Preferences standardPreferences];
 	if (!prefs.enableMinimumFontSize)
-		defaultWebPrefs.minimumFontSize = 1;
+		[TabbedWebView defaultWebPrefs].minimumFontSize = [TabbedWebView passiveWebPrefs].minimumFontSize = 1;
 	else
 	{
 		NSInteger size = prefs.minimumFontSize;
-		defaultWebPrefs.minimumFontSize = (int)size;
+		[TabbedWebView defaultWebPrefs].minimumFontSize = [TabbedWebView passiveWebPrefs].minimumFontSize = (int)size;
 	}
 }
 
@@ -380,16 +406,24 @@ -(void)scrollToTop
 -(void)loadUseJavaScript
 {
 	Preferences * prefs = [Preferences standardPreferences];
-	defaultWebPrefs.javaScriptEnabled = prefs.useJavaScript;
+	[TabbedWebView defaultWebPrefs].javaScriptEnabled = prefs.useJavaScript;
 }
 
 /* loadUseWebPlugins
- * Sets up the web preferences for using JavaScript.
+ * Sets up the web preferences for using WebPlugins.
  */
 -(void)loadUseWebPlugins
 {
     Preferences * prefs = [Preferences standardPreferences];
-    defaultWebPrefs.plugInsEnabled = prefs.useWebPlugins;
+    [TabbedWebView defaultWebPrefs].plugInsEnabled = prefs.useWebPlugins;
+}
+
+/* abortJavascriptAndPlugIns
+ * Sets up the web preferences to stop JavaScript and WebPlugins
+ */
+-(void)abortJavascriptAndPlugIns
+{
+    self.preferences = [TabbedWebView passiveWebPrefs];
 }
 
 /* keyDown