Adds customizable user script and user stylesheet.

App/Web Process Bundle Bridge/SBRProcessBundleBridge.h

@@ -45,6 +45,8 @@ NS_SWIFT_NAME(ProcessBundleBridge)
 
 - (void)parseDocumentForReaderMode:(void(^)(NSString *))completionBlock NS_SWIFT_NAME(parseDocumentForReaderMode(completion:));
 
+- (void)reloadCustomizedUserScriptsAndStylesheets;
+
 - (instancetype)init NS_UNAVAILABLE;
 
 @end

App/Web Process Bundle Bridge/SBRProcessBundleBridge.m

@@ -34,6 +34,10 @@
     WKUserScript          *_readabilityScript;
     
     NSArray<WKUserScript *> *_userScripts;
+    
+    // These come from settings. 
+    _WKUserStyleSheet *_customizedUserStylesheet;
+    WKUserScript      *_customizedUserScript;
 }
 
 - (void)tearDown
@@ -101,6 +105,9 @@
             [userContentController addUserScript:script];
         }
         
+        // Reload customized user scripts/stylesheets from settings
+        [self reloadCustomizedUserScriptsAndStylesheets];
+        
         // Instantiate web view
         WKWebView *webView = [[WKWebView alloc] initWithFrame:CGRectZero configuration:webViewConfiguration];
         
@@ -135,6 +142,30 @@
     return _userScripts;
 }
 
+- (void)reloadCustomizedUserScriptsAndStylesheets
+{
+    WKUserContentController *userContentController = [_webViewConfiguration userContentController];
+    if (_customizedUserScript) {
+        [userContentController _removeUserScript:_customizedUserScript];
+    }
+    
+    NSString *scriptSource = [[NSUserDefaults standardUserDefaults] stringForKey:@"userScript"];
+    if ([scriptSource length]) {
+        _customizedUserScript = [[WKUserScript alloc] initWithSource:scriptSource injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly:YES];
+        [userContentController addUserScript:_customizedUserScript];
+    }
+    
+    if (_customizedUserStylesheet) {
+        [userContentController _removeUserStyleSheet:_customizedUserStylesheet];
+    }
+    
+    NSString *stylesheetSource = [[NSUserDefaults standardUserDefaults] stringForKey:@"userStylesheet"];
+    if ([stylesheetSource length]) {
+        _customizedUserStylesheet = [[_WKUserStyleSheet alloc] initWithSource:stylesheetSource forMainFrameOnly:YES];
+        [userContentController _addUserStyleSheet:_customizedUserStylesheet];
+    }
+}
+
 #pragma mark <SBRWebProcessDelegate>
 
 - (void)webProcessDidConnect