Add infrastructure for accessing "unstable" content providers.

We have an API and some stuff that purports to this, but no real
implementation yet.

Change-Id: I93555440014a50fdf79fa3f65318d90fb82265b4
diff --git a/core/java/android/app/ContextImpl.java b/core/java/android/app/ContextImpl.java
index 4943c9a..299e408 100644
--- a/core/java/android/app/ContextImpl.java
+++ b/core/java/android/app/ContextImpl.java
@@ -1692,6 +1692,16 @@
             return mMainThread.releaseProvider(provider);
         }
 
+        @Override
+        protected IContentProvider acquireUnstableProvider(Context c, String name) {
+            return mMainThread.acquireUnstableProvider(c, name);
+        }
+
+        @Override
+        public boolean releaseUnstableProvider(IContentProvider icp) {
+            return mMainThread.releaseUnstableProvider(icp);
+        }
+
         private final ActivityThread mMainThread;
     }
 }