ash: Clean up SetTabletModeEnabledForTest

The wait_for_completion parameter is unused. Remove it.

Bug: none
Change-Id: Ifef5cb2a3fab2cd96d7ce0515384b15c262c399d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625982
Auto-Submit: James Cook <jamescook@chromium.org>
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843062}

ash/public/cpp/test/shell_test_api.h

@@ -64,10 +64,8 @@ class ASH_EXPORT ShellTestApi {
 
   // Enables or disables the tablet mode. TabletMode switch can be
   // asynchronous, and this will wait until the transition is complete
-  // by default. Set |wait_for_completion| to false if you do not want
-  // to wait.
-  void SetTabletModeEnabledForTest(bool enable,
-                                   bool wait_for_completion = true);
+  // by default.
+  void SetTabletModeEnabledForTest(bool enable);
 
   // Enables the keyboard and associates it with the primary root window
   // controller. In tablet mode, enables the virtual keyboard.

ash/shell_test_api.cc

@@ -157,8 +157,7 @@ bool ShellTestApi::IsSystemModalWindowOpen() {
   return Shell::IsSystemModalWindowOpen();
 }
 
-void ShellTestApi::SetTabletModeEnabledForTest(bool enable,
-                                               bool wait_for_completion) {
+void ShellTestApi::SetTabletModeEnabledForTest(bool enable) {
   // Detach mouse devices, so we can enter tablet mode.
   // Calling RunUntilIdle() here is necessary before setting the mouse devices
   // to prevent the callback from evdev thread from overwriting whatever we set