Closure compile task_contoller_unittest

 - remove task_contoller_unittest.html
 - add BUILD rules to auto-generate and compile this unittest
 - define, install, and use mockChrome in the unittest code
 - use setupFileManagerPrivate() in all test cases
   - testExecuteEntryTask had its own local version but the
     test could also jsut use the common one: make it so.
 - make all test cases use the createTaskController helper
   - update JsDoc: a {FileSelectionHandler} is now required
   - remove the crostini create helper function
   - remove crostini.init call: no test cases depend on the
     crostini volume manager fake.
   - make createTaskController call createCrostiniForTest()
     when new-ing the {TaskController}.
 - make MockFileSelectionHandler @constructor, and @extends
   {FileSelectionHandler} interface, so createTaskController
   construction is both simple and type-safe.
 - add decriptive comments for each test case fixture
 - fix all Closure compiler errors, and auto-format JS code

No change in test behavior, no new tests.

Bug: 912410
Change-Id: I7a685533632860ce785b9aaca2e84b7c69579979
Reviewed-on: https://chromium-review.googlesource.com/c/1364270
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614276}
4 files changed