Fix issue #6603152: User-adjustable autobrightness broken?

Two issues:
- The new brightness was not being applied when switching out
  of auto-brightness mode.
- We were resetting to the last brightness level when switching
  modes.  This is because at that point we read the current
  brightness setting, but that isn't changed as the user adjusts
  only when the final value is committed.  To fix this, we have
  a new local variable keeping track of the last brightness value
  we have shown and use that when we haven't committed the
  brightness to settings.

Change-Id: I7cc02c9f90128eacec427587a3f6b8f25ede4bd3
diff --git a/src/com/android/settings/BrightnessPreference.java b/src/com/android/settings/BrightnessPreference.java
index c80f66d..eff5c50 100644
--- a/src/com/android/settings/BrightnessPreference.java
+++ b/src/com/android/settings/BrightnessPreference.java
@@ -47,6 +47,8 @@
     private boolean mAutomaticAvailable;
     private boolean mAutomaticMode;
 
+    private int mCurBrightness = -1;
+
     private boolean mRestoredOldState;
 
     // Backlight range is from 0 - 255. Need to make sure that user
@@ -60,6 +62,7 @@
     private ContentObserver mBrightnessObserver = new ContentObserver(new Handler()) {
         @Override
         public void onChange(boolean selfChange) {
+            mCurBrightness = -1;
             onBrightnessChanged();
         }
     };
@@ -135,6 +138,7 @@
                 : Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL);
         mSeekBar.setProgress(getBrightness());
         mSeekBar.setEnabled(!mAutomaticMode);
+        setBrightness(mSeekBar.getProgress(), false);
     }
 
     private int getBrightness() {
@@ -145,8 +149,12 @@
                     Settings.System.SCREEN_AUTO_BRIGHTNESS_ADJ, 0);
             brightness = (brightness+1)/2;
         } else {
-            brightness = Settings.System.getInt(getContext().getContentResolver(),
-                    Settings.System.SCREEN_BRIGHTNESS, 100);
+            if (mCurBrightness < 0) {
+                brightness = Settings.System.getInt(getContext().getContentResolver(),
+                        Settings.System.SCREEN_BRIGHTNESS, 100);
+            } else {
+                brightness = mCurBrightness;
+            }
             brightness = (brightness - mScreenBrightnessDim)
                     / (MAXIMUM_BACKLIGHT - mScreenBrightnessDim);
         }
@@ -199,6 +207,7 @@
         }
         setBrightness(mOldBrightness, false);
         mRestoredOldState = true;
+        mCurBrightness = -1;
     }
 
     private void setBrightness(int brightness, boolean write) {
@@ -229,9 +238,12 @@
                     power.setBacklightBrightness(brightness);
                 }
                 if (write) {
+                    mCurBrightness = -1;
                     final ContentResolver resolver = getContext().getContentResolver();
                     Settings.System.putInt(resolver,
                             Settings.System.SCREEN_BRIGHTNESS, brightness);
+                } else {
+                    mCurBrightness = brightness;
                 }
             } catch (RemoteException doe) {
             }
@@ -255,6 +267,7 @@
         myState.progress = mSeekBar.getProgress();
         myState.oldAutomatic = mOldAutomatic == 1;
         myState.oldProgress = mOldBrightness;
+        myState.curBrightness = mCurBrightness;
 
         // Restore the old state when the activity or dialog is being paused
         restoreOldState();
@@ -275,6 +288,7 @@
         mOldAutomatic = myState.oldAutomatic ? 1 : 0;
         setMode(myState.automatic ? 1 : 0);
         setBrightness(myState.progress, false);
+        mCurBrightness = myState.curBrightness;
     }
 
     private static class SavedState extends BaseSavedState {
@@ -283,6 +297,7 @@
         boolean oldAutomatic;
         int progress;
         int oldProgress;
+        int curBrightness;
 
         public SavedState(Parcel source) {
             super(source);
@@ -290,6 +305,7 @@
             progress = source.readInt();
             oldAutomatic = source.readInt() == 1;
             oldProgress = source.readInt();
+            curBrightness = source.readInt();
         }
 
         @Override
@@ -299,6 +315,7 @@
             dest.writeInt(progress);
             dest.writeInt(oldAutomatic ? 1 : 0);
             dest.writeInt(oldProgress);
+            dest.writeInt(curBrightness);
         }
 
         public SavedState(Parcelable superState) {