Add commands to Chrome WebDriver for installing and manipulating extensions.

chrome/test/webdriver/test/infobar_browser_action_extension/bg.html

Index: chrome/test/webdriver/test/infobar_browser_action_extension/bg.html
diff --git a/chrome/test/webdriver/test/infobar_browser_action_extension/bg.html b/chrome/test/webdriver/test/infobar_browser_action_extension/bg.html
new file mode 100644
index 0000000000000000000000000000000000000000..20cea3cb96aa4297592f9da903d75cce84f4cb36
--- /dev/null
+++ b/chrome/test/webdriver/test/infobar_browser_action_extension/bg.html
@@ -0,0 +1,18 @@
+<script>
+  var g_infobarReady = false;
+  var g_callback = null;
+  function waitForInfobar(callback) {
+    if (g_infobarReady)
+      callback();
+    g_callback = callback;
+  }
+
+  chrome.tabs.create({'url': 'view_checks.html'}, function(tab) {
+    chrome.experimental.infobars.show(
+        {'tabId': tab.id, 'path': 'view_checks.html'}, function() {
+      g_infobarReady = true;
+      if (g_callback)
+        g_callback();
+    });
+  });
+</script>