Dynamic fonts (#3698)

* Piping themes into the renderer and ensuring fields update their size information when constants change.

core/theme_manager.js

@@ -94,6 +94,10 @@ Blockly.ThemeManager.prototype.setTheme = function(theme) {
   // Refresh all subscribed workspaces.
   for (var i = 0, workspace; (workspace = this.subscribedWorkspaces_[i]); i++) {
     workspace.refreshTheme();
+    // Re-render if workspace is visible
+    if (workspace.isVisible()) {
+      workspace.setVisible(true);
+    }
   }
 
   // Refresh all registered Blockly UI components.