Reenable DevToolsSanityTest.TestDeviceEmulation.

BUG=397889
TBR=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/564763002

Cr-Commit-Position: refs/heads/master@{#294375}

chrome/browser/devtools/devtools_sanity_browsertest.cc

@@ -790,8 +790,7 @@ IN_PROC_BROWSER_TEST_F(DevToolsSanityTest, MAYBE_TestConsoleOnNavigateBack) {
   RunTest("testConsoleOnNavigateBack", kNavigateBackTestPage);
 }
 
-// https://crbug.com/397889
-IN_PROC_BROWSER_TEST_F(DevToolsSanityTest, DISABLED_TestDeviceEmulation) {
+IN_PROC_BROWSER_TEST_F(DevToolsSanityTest, TestDeviceEmulation) {
   RunTest("testDeviceMetricsOverrides", "about:blank");
 }