Implement background vs foreground broadcasts

Before now, receiving a broadcast would cause a process to be hoisted
to foreground priority / cgroup.  This is no longer the case: broadcasts
by default are handled in the background, with a suitably increased
timeout interval.  When a given broadcast needs to be dealt with in a
more timely manner, the issuer can set the new FLAG_BROADCAST_FOREGROUND
flag on the Intent, which will produce the old foreground-priority
behavior.

To avoid priority inversions, foreground broadcasts are tracked on a
separate outgoing queue and can be in flight simultaneously with a
background-priority broadcast.  If there is already a background-level
broadcast in flight to a given app and then a foreground-level one is
dispatched to that app, the app [and its handling of both broadcasts]
will be properly hoisted to foreground priority.

This change is also essentially the first step towards refactoring the
broadcast-handling portions of the Activity Manager into a more
independent existence.  Making BroadcastQueue a top-level class and
regularizing its operation viz the primary Activity Manager operation
is the next step.

Change-Id: If1be33156dc22dcce318edbb5846b08df8e7bed5

Author: Christopher Tate

api/current.txt

@@ -5640,6 +5640,7 @@ package android.content {
     field public static final int FLAG_GRANT_READ_URI_PERMISSION = 1; // 0x1
     field public static final int FLAG_GRANT_WRITE_URI_PERMISSION = 2; // 0x2
     field public static final int FLAG_INCLUDE_STOPPED_PACKAGES = 32; // 0x20
+    field public static final int FLAG_RECEIVER_FOREGROUND = 268435456; // 0x10000000
     field public static final int FLAG_RECEIVER_REGISTERED_ONLY = 1073741824; // 0x40000000
     field public static final int FLAG_RECEIVER_REPLACE_PENDING = 536870912; // 0x20000000
     field public static final java.lang.String METADATA_DOCK_HOME = "android.dock_home";

core/java/android/content/Intent.java

@@ -2956,6 +2956,13 @@ public static Intent createChooser(Intent target, CharSequence title) {
      * to their receivers.
      */
     public static final int FLAG_RECEIVER_REPLACE_PENDING = 0x20000000;
+    /**
+     * If set, when sending a broadcast the recipient is allowed to run at
+     * foreground priority, with a shorter timeout interval.  During normal
+     * broadcasts the receivers are not automatically hoisted out of the
+     * background priority class.
+     */
+    public static final int FLAG_RECEIVER_FOREGROUND = 0x10000000;
     /**
      * If set, when sending a broadcast <i>before boot has completed</i> only
      * registered receivers will be called -- no BroadcastReceiver components
@@ -2969,14 +2976,14 @@ public static Intent createChooser(Intent target, CharSequence title) {
      *
      * @hide
      */
-    public static final int FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT = 0x10000000;
+    public static final int FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT = 0x08000000;
     /**
      * Set when this broadcast is for a boot upgrade, a special mode that
      * allows the broadcast to be sent before the system is ready and launches
      * the app process with no providers running in it.
      * @hide
      */
-    public static final int FLAG_RECEIVER_BOOT_UPGRADE = 0x08000000;
+    public static final int FLAG_RECEIVER_BOOT_UPGRADE = 0x04000000;
 
     /**
      * @hide Flags that can't be changed with PendingIntent.