Make GET_TASKS signature|system.

Normal apps can't hold it now.  If they try to use
getRecentTasks() or getRunningTasks() without the permission,
they will only see their own tasks and home in the list.

Also took this opportunity to eradicate all of the old pending
thumbnail stuff.

Change-Id: I6dc52a06221c78097162e4a8b482027b798bf3ee
diff --git a/CleanSpec.mk b/CleanSpec.mk
index c6f6a62..c841338 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -190,6 +190,7 @@
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/framework-base_intermediates/src/core/java/android/view/IMagnificationCallbacks*)
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/framework-base_intermediates/src/core/java/android/tv/)
 $(call add-clean-step, rm -rf $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/framework-base_intermediates/src/media/java/android/media/)
+$(call add-clean-step, rm -rf $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/framework-base_intermediates/src/core/java/android/app)
 
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST