Do not use last app rotation as default.

If the rotation sensor has been disabled we were substituting the
last app rotation for the sensor value. This fix uses the last
sensor value delivered before the sensor was disabled. Only use
the last app rotation if we never have received a valid sensor
value.

Fixes bug 6387946.

Change-Id: I50743c30ee2b4455e9848d3a619809be97eec3c8

Author: Craig Mautner

policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

@@ -361,6 +361,7 @@ public class PhoneWindowManager implements WindowManagerPolicy {
     boolean mScreenOnEarly = false;
     boolean mScreenOnFully = false;
     boolean mOrientationSensorEnabled = false;
+    int mLastSensorRotation = -1;
     int mCurrentAppOrientation = ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED;
     boolean mHasSoftInput = false;
 
@@ -3728,7 +3729,16 @@ public int rotationForOrientationLw(int orientation, int lastRotation) {
         synchronized (mLock) {
             int sensorRotation = mOrientationListener.getProposedRotation(); // may be -1
             if (sensorRotation < 0) {
-                sensorRotation = lastRotation;
+                // Sensor is disabled, device probably just turned off.
+                if (mLastSensorRotation >= 0) {
+                    sensorRotation = mLastSensorRotation;
+                } else {
+                    // Sensor has never been enabled. Last resort is to use lastRotation.
+                    sensorRotation = lastRotation;
+                }
+            } else {
+                // Valid sensor data, save it away.
+                mLastSensorRotation = sensorRotation;
             }
 
             final int preferredRotation;