Hide cursor when auto-capturing screen

On a testimage build, the screen sharing permission dialog is
automatically dismissed to allow Android CTS tests to record the screen.
These tests do not expect to record the mouse cursor, so make sure it is
automatically turned off at the same time.

Bug: b:118833026
Test: CTS CtsViewTestCases passes on non-tablet devices
Change-Id: I1633d270c01838e60b50a2370483452e829d1361
Reviewed-on: https://chromium-review.googlesource.com/c/1343358Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Commit-Queue: Benjamin Gordon <bmgordon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609480}

chrome/browser/chromeos/arc/screen_capture/arc_screen_capture_bridge.cc

@@ -170,6 +170,10 @@ void ArcScreenCaptureBridge::TestModeAcceptPermission(
   pending_permissions_map_.erase(found);
   // The dialog will be closed when 'found' goes out of scope and is
   // destructed and the dialog within it is destructed.
+
+  // If we're auto-sharing the screen in test mode, we don't want to record
+  // the cursor, so turn it off.
+  ash::Shell::Get()->cursor_manager()->HideCursor();
 }
 
 void ArcScreenCaptureBridge::OpenSession(