Fix an event injection bug when the policy is bypassed.

Added the concept of a "trusted" event to distinguish between events from
attached input devices or trusted injectors vs. other applications.
This change enables us to move certain policy decisions out of the
dispatcher and into the policy itself where they can be handled more
systematically.

Cherry pick of b931a1b4 from gingerbread into master.

Change-Id: I700a5f07b8b227878cea9437a289a45a245c0424
diff --git a/include/ui/Input.h b/include/ui/Input.h
index 66061fd..8c6018b 100644
--- a/include/ui/Input.h
+++ b/include/ui/Input.h
@@ -95,6 +95,10 @@
     // Indicates that the input event was injected.
     POLICY_FLAG_INJECTED = 0x01000000,
 
+    // Indicates that the input event is from a trusted source such as a directly attached
+    // input device or an application with system-wide event injection permission.
+    POLICY_FLAG_TRUSTED = 0x02000000,
+
     /* These flags are set by the input reader policy as it intercepts each event. */
 
     // Indicates that the screen was off when the event was received and the event