title: Chrome pageAction icon not showing except when debugging
body: <p>I'm trying to get a Chrome pageAction icon to appear, but it only briefly flashes up as a page loads and then disappears.</p>
  
  <p>However, the thing that has me flummoxed is that when I use the Dev Tools debugger and stick a break-point on the chrome.pageAction.show() call, it works perfectly! Here's my manifest.json:</p>
  
  <pre><code>{
      "manifest_version": 2,
      "name": "20130409-test",
      "description": "Page action icons don't work!",
      "version": "0.1",
      "icons": {"16": "icon16.png", "48": "icon48.png", "128": "icon128.png"},
      "background": {
          "scripts": ["background.js"],
          "persistent": true
      },
      "permissions": [
          "&lt;all_urls&gt;",
          "webRequest",
          "webRequestBlocking"
      ],
      "page_action": {
          "default_icon": {
              "19": "icon19.png",
              "38": "icon38.png"
          },
          "default_title": "Page action title here!"
      }
  }
  </code></pre>
  
  <p>And my background.js page is:</p>
  
  <pre><code>chrome.webRequest.onSendHeaders.addListener(
      function(details) {
          chrome.pageAction.show(details.tabId);
          chrome.pageAction.setTitle({
              "tabId": details.tabId,
              "title": "url=" + details.url
          });
      },
      {urls: ["&lt;all_urls&gt;"], types: ["main_frame"]},
      ["requestHeaders"]
  );
  </code></pre>