StrictMode: now in more system server threads.

Who knew there were so many Loopers in the system server?

This adds dropbox logging for the activity manager thread, policy
thread, and window manager thread.

The goal's to catch more stuttering.

Change-Id: I999a6ff4a955f0ef549b12a38796b843ade5fe66
diff --git a/services/java/com/android/server/am/ActivityManagerService.java b/services/java/com/android/server/am/ActivityManagerService.java
index 7905dc6..ba8d7d2 100644
--- a/services/java/com/android/server/am/ActivityManagerService.java
+++ b/services/java/com/android/server/am/ActivityManagerService.java
@@ -1349,6 +1349,11 @@
                 }
             }
 
+            // For debug builds, log event loop stalls to dropbox for analysis.
+            if (StrictMode.conditionallyEnableDebugLogging()) {
+                Slog.i(TAG, "Enabled StrictMode logging for AThread's Looper");
+            }
+
             Looper.loop();
         }
     }