title: Chrome extension content script is not injecting in to most pages
body: <p>I'm trying to build a basic extension that injects an alert script in to every page loaded. But it seems that the script is injecting only to <em>some</em> pages (most pages it's not injected in to), and I couldn't find a pattern in how it picks the pages to get injected to.</p>
  
  <p>This is the manifest:</p>
  
  <pre><code>  {
          "name": "TestingTest",
          "version": "0.1.1",
          "description": "Testing Tests!",
          "manifest_version": 2,
          "content_scripts": [
              {
                  "matches": ["http://*/", "https://*/"],
                  "js": ["content.js"],
                  "run_at": "document_end"
              }
          ],
          "background": {
              "page": "background.html"
          },
          "permissions": [
              "tabs",
              "http://*/", "https://*/",
              "cookies"
          ],
          "icons": {
              "16": "my_icon_64.png",
              "32": "my_icon_64.png",
              "48": "my_icon_64.png",
              "128": "my_icon_64.png"
          }
      }
  </code></pre>
  
  <p>and this is <code>ccontent.js</code>:</p>
  
  <pre><code>alert("content script");
  console.log("content script")
  </code></pre>
  
  <p>I'm getting the alert only on a select few pages. The pages that it's injected in to seem to vary if I load the extension in different Chrome profiles.</p>