Allow stacks to hold tasks on various sizes.

Tasks are now resizeable just like stacks. Adjusting the size
of a stack will also adjust the size of all it's containing
tasks. This model allows us to be more flexible
in using stacks as workspaces (like you would have in a
desktop environment) and tasks as the resizeable windows
within the workspace.

Also added "adb shell dumpsys window visible-apps" for
getting the list of visible app windows.

Bug: 22068114
Bug: 19182363

Change-Id: I5bf77063252a5abae4e327f6fc42e607091749f9
diff --git a/services/core/java/com/android/server/EventLogTags.logtags b/services/core/java/com/android/server/EventLogTags.logtags
index daf1751..13b3f8d 100644
--- a/services/core/java/com/android/server/EventLogTags.logtags
+++ b/services/core/java/com/android/server/EventLogTags.logtags
@@ -158,7 +158,7 @@
 # Task removed with source explanation.
 31003 wm_task_removed (TaskId|1|5),(Reason|3)
 # Stack created.
-31004 wm_stack_created (StackId|1|5),(RelativeBoxId|1|5),(Position|1),(Weight|1|6)
+31004 wm_stack_created (StackId|1|5)
 # Home stack moved to top (1) or bottom (0).
 31005 wm_home_stack_moved (ToTop|1)
 # Stack removed.