WebUI: Include cr/ui/grid.js only on ChromeOS.

Not used in any other platform.

Bug: None
Change-Id: I13cb2550ee38a828d8d266aeea5a8aa04695b54e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1638915
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Esmael El-Moslimany <aee@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665766}
  void RunTest(const GURL& url) {
    ui_test_utils::NavigateToURL(browser(), url);
    content::WebContents* web_contents =
        browser()->tab_strip_model()->GetActiveWebContents();
    ASSERT_TRUE(web_contents);
    EXPECT_TRUE(ExecuteWebUIResourceTest(web_contents, include_libraries_));
  }

  void RunTest(const GURL& url) {
    ui_test_utils::NavigateToURL(browser(), url);
    content::WebContents* web_contents =
        browser()->tab_strip_model()->GetActiveWebContents();
    ASSERT_TRUE(web_contents);
    EXPECT_TRUE(ExecuteWebUIResourceTest(web_contents, include_libraries_));
  }
