Convert the autofill interactive browser test to a normal browser_test. I added testing methods to fake input events that don't depend on the OS and being at the front.

BUG=121574
Review URL: https://chromiumcodereview.appspot.com/10368010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@135432 0039d316-1c4b-4281-b951-d872f2087c98
  void ExpectFieldValue(const std::wstring& field_name,
                        const std::string& expected_value) {
    std::string value;
    ASSERT_TRUE(ui_test_utils::ExecuteJavaScriptAndExtractString(
        browser()->GetSelectedWebContents()->GetRenderViewHost(), L"",
        L"window.domAutomationController.send("
        L"document.getElementById('" + field_name + L"').value);", &value));
    EXPECT_EQ(expected_value, value);
  }

  void ExpectFieldValue(const std::wstring& field_name,
                        const std::string& expected_value) {
    std::string value;
    ASSERT_TRUE(ui_test_utils::ExecuteJavaScriptAndExtractString(
        browser()->GetSelectedWebContents()->GetRenderViewHost(), L"",
        L"window.domAutomationController.send("
        L"document.getElementById('" + field_name + L"').value);", &value));
    EXPECT_EQ(expected_value, value);
  }
