background.js

chrome.runtime.onInstalled.addListener(() => {
  chrome.storage.local.set({ vPos: 300, fSize: 24, fColor: "#FFFFFF" });

  chrome.declarativeContent.onPageChanged.removeRules(undefined, () => {
    chrome.declarativeContent.onPageChanged.addRules([
      {
        conditions: [
          new chrome.declarativeContent.PageStateMatcher({
            pageUrl: { hostSuffix: "netflix.com" }
          })
        ],
        actions: [new chrome.declarativeContent.ShowPageAction()]
      }
    ]);
  });
});

chrome.tabs.onUpdated.addListener((tabId, changeInfo, tab) => {
  if (changeInfo.status === "complete" && tab.active) {
    chrome.storage.local.get(["vPos", "fSize", "fColor"], data => {
      chrome.tabs.executeScript(
        tabId,
        {
          file: "script.js"
        },
        () => {
          const error = chrome.runtime.lastError;
          if (error) "Error. Tab ID: " + tab.id + ": " + JSON.stringify(error);

          chrome.tabs.sendMessage(tabId, {
            vPos: data.vPos,
            fSize: data.fSize,
            fColor: data.fColor
          });
        }
      );
    });
  }
});