Adding sharedPref for blocked number migration

+ Users are shown a dialog when they're running on an SDK which
supports the framework blocking solution, but they haven't yet
migrated. In order to determine whether the user has migrated or not,
a SharedPreference value is used. In a later CL which performs the
migration, this value will be updated as the final step.

Bug: 26664600
Change-Id: I5a12be643d0fb3b52ef408215779423bf0a2ddc7
diff --git a/src/com/android/dialer/DialerApplication.java b/src/com/android/dialer/DialerApplication.java
index 078b551..189c682 100644
--- a/src/com/android/dialer/DialerApplication.java
+++ b/src/com/android/dialer/DialerApplication.java
@@ -17,16 +17,23 @@
 package com.android.dialer;
 
 import android.app.Application;
+import android.content.Context;
 import android.os.Trace;
+import android.support.annotation.Nullable;
 
 import com.android.contacts.common.extensions.ExtensionsFactory;
+import com.android.contacts.common.testing.NeededForTesting;
+import com.android.dialer.compat.FilteredNumberCompat;
 
 public class DialerApplication extends Application {
 
     private static final String TAG = "DialerApplication";
 
+    private static Context sContext;
+
     @Override
     public void onCreate() {
+        sContext = this;
         Trace.beginSection(TAG + " onCreate");
         super.onCreate();
         Trace.beginSection(TAG + " ExtensionsFactory initialization");
@@ -34,4 +41,14 @@
         Trace.endSection();
         Trace.endSection();
     }
+
+    @Nullable
+    public static Context getContext() {
+        return sContext;
+    }
+
+    @NeededForTesting
+    public static void setContextForTest(Context context) {
+        sContext = context;
+    }
 }