Fix the flaky failure of WebContentsImplBrowserTest.PausePageScheduledTasks

The flaky failure of the test seems to be due to not waiting long enough after
resuming work again. This Cl changes the workaround logic to actually wait until
the javascript work again (or let the test fail by timing out otherwise).

Bug: 832191
Change-Id: I3c2f04ccf4d00cee6505e607566628d690f4ef00
Reviewed-on: https://chromium-review.googlesource.com/1011744
Commit-Queue: Gyuyoung Kim <gyuyoung.kim@lge.com>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553927}

content/browser/web_contents/web_contents_impl_browsertest.cc

@@ -2240,14 +2240,7 @@ IN_PROC_BROWSER_TEST_F(WebContentsImplBrowserTest, UpdateLoadState) {
   waiter.Wait(net::LOAD_STATE_IDLE, base::string16());
 }
 
-// Disabled due to flakes on Linux. https://crbug.com/832191
-#if defined(OS_LINUX)
-#define MAYBE_PausePageScheduledTasks DISABLED_PausePageScheduledTasks
-#else
-#define MAYBE_PausePageScheduledTasks PausePageScheduledTasks
-#endif
-IN_PROC_BROWSER_TEST_F(WebContentsImplBrowserTest,
-                       MAYBE_PausePageScheduledTasks) {
+IN_PROC_BROWSER_TEST_F(WebContentsImplBrowserTest, PausePageScheduledTasks) {
   EXPECT_TRUE(embedded_test_server()->Start());
 
   GURL test_url = embedded_test_server()->GetURL("/pause_schedule_task.html");
@@ -2283,14 +2276,17 @@ IN_PROC_BROWSER_TEST_F(WebContentsImplBrowserTest,
   // Resume the paused blink schedule tasks.
   shell()->web_contents()->PausePageScheduledTasks(false);
 
-  // We call a document.getElementById five times in order to give the
-  // javascript time to run with DOM again.
-  for (int i = 0; i < 5; i++) {
+  // Wait for an amount of time in order to give the javascript time to
+  // work again. If the javascript doesn't work again, the test will fail due to
+  // the time out.
+  while (true) {
     EXPECT_TRUE(content::ExecuteScriptAndExtractInt(
         shell(),
         "domAutomationController.send(document.getElementById('textfield')."
         "value.length)",
         &next_text_length));
+    if (next_text_length > text_length)
+      break;
   }
 
   EXPECT_TRUE(content::ExecuteScriptAndExtractInt(