Revert of Disable flaky TaskManagerBrowserTest.DevToolsNew{Und,D}ockedWindow...

Revert of Disable flaky TaskManagerBrowserTest.DevToolsNew{Und,D}ockedWindow tests (patchset #1 id:1 of https://codereview.chromium.org/2301493002/ )

Reason for revert:
The bug is now fixed so disabling these tests is no longer needed.
See https://codereview.chromium.org/2293293002/

Original issue's description:
> Disable flaky TaskManagerBrowserTest.DevToolsNew{Und,D}ockedWindow tests
>
> BUG=642482
> TBR=stanisc@chromium.org,nick@chromium.org:
>
> Committed: https://crrev.com/a01d97dff593c530fe6b204421bdaa39252801e9
> Cr-Commit-Position: refs/heads/master@{#415595}

TBR=nick@chromium.org,battre@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=642482

Review-Url: https://codereview.chromium.org/2298213003
Cr-Commit-Position: refs/heads/master@{#415747}

chrome/browser/task_manager/task_manager_browsertest.cc

@@ -700,9 +700,7 @@ IN_PROC_BROWSER_TEST_F(TaskManagerUtilityProcessBrowserTest,
       WaitForTaskManagerRows(1, MatchUtility(proxy_resolver_name)));
 }
 
-// TODO(crbug.com/642482): Disabled flaky test.
-IN_PROC_BROWSER_TEST_F(TaskManagerBrowserTest,
-                       DISABLED_DevToolsNewDockedWindow) {
+IN_PROC_BROWSER_TEST_F(TaskManagerBrowserTest, DevToolsNewDockedWindow) {
   ShowTaskManager();  // Task manager shown BEFORE dev tools window.
 
   ASSERT_NO_FATAL_FAILURE(WaitForTaskManagerRows(1, MatchAnyTab()));
@@ -713,9 +711,7 @@ IN_PROC_BROWSER_TEST_F(TaskManagerBrowserTest,
   DevToolsWindowTesting::CloseDevToolsWindowSync(devtools);
 }
 
-// TODO(crbug.com/642482): Disabled flaky test.
-IN_PROC_BROWSER_TEST_F(TaskManagerBrowserTest,
-                       DISABLED_DevToolsNewUndockedWindow) {
+IN_PROC_BROWSER_TEST_F(TaskManagerBrowserTest, DevToolsNewUndockedWindow) {
   ShowTaskManager();  // Task manager shown BEFORE dev tools window.
   ASSERT_NO_FATAL_FAILURE(WaitForTaskManagerRows(1, MatchAnyTab()));
   DevToolsWindow* devtools =