Compatibility fix for apps that construct Notification.Builders early

Some apps in the wild are known to construct a Notification.Builder
from within their Activity constructor, passing said Activity instance
as the Context parameter. However at this point in the Activity's
lifecycle the ContextWrapper's base context has not yet been populated
and most calls to Context methods will fail.

Even though this was technically undefined behavior in the past, as
apps have little to no way to guess at these internal implementation
details it's probably best to preserve old expectations. Add a note
in Notification.Builder for future framework developers and remove the
offending call - the associated field was never used anyway.

ಠ_ಠ

Change-Id: I4cf3df10be14739babc8ae9a969d261a7ecf8beb

core/java/android/app/Notification.java

@@ -1671,7 +1671,6 @@ public class Notification implements Parcelable
         private Notification mPublicVersion = null;
         private final NotificationColorUtil mColorUtil;
         private ArrayList<String> mPeople;
-        private boolean mPreQuantum;
         private int mColor = COLOR_DEFAULT;
 
         /**
@@ -1694,6 +1693,15 @@ public class Notification implements Parcelable
          *            object.
          */
         public Builder(Context context) {
+            /*
+             * Important compatibility note!
+             * Some apps out in the wild create a Notification.Builder in their Activity subclass
+             * constructor for later use. At this point Activities - themselves subclasses of
+             * ContextWrapper - do not have their inner Context populated yet. This means that
+             * any calls to Context methods from within this constructor can cause NPEs in existing
+             * apps. Any data populated from mContext should therefore be populated lazily to
+             * preserve compatibility.
+             */
             mContext = context;
 
             // Set defaults to match the defaults of a Notification
@@ -1702,7 +1710,6 @@ public class Notification implements Parcelable
             mPriority = PRIORITY_DEFAULT;
             mPeople = new ArrayList<String>();
 
-            mPreQuantum = context.getApplicationInfo().targetSdkVersion < Build.VERSION_CODES.L;
             mColorUtil = NotificationColorUtil.getInstance();
         }