Move MockWebContentsTaskManager into its own file.
[splitting apart task_manager_browsertest_util, part 1 of 6]
Move MockWebContentsTaskManager into its own file, and compile it
only into the browser_tests target.
Remove the mostly redundant task manager PanelBrowserTests
(these are actually interactive_ui_tests). Extend
TaskManagerBrowserTest.NoticePanel to replace lost coverage.
BUG=
606963
Committed:
https://crrev.com/25814be52a98fde4623a239cd847bfbbc54a6df0
Cr-Commit-Position: refs/heads/master@{#392428}