report stack of lock owner to crashlytics when can't get it

I'm seeing something permanently lock a game so it can't be opened. So
add code to report the stack of the owner to Crashlytics when opening
fails 3 times in a row. It's stubbed out for non-debug builds.

xwords4/android/app/build.gradle

@@ -70,6 +70,7 @@ android {
             resValue "string", "invite_prefix", "/and/"
             buildConfigField "int[]", "SMS_BANNED_EXPL", "null"
 			buildConfigField "boolean", "UDP_ENABLED", "true"
+			buildConfigField "boolean", "REPORT_LOCKS", "false"
         }
 
         xw4 {
@@ -104,6 +105,7 @@ android {
             buildConfigField "boolean", "WIDIR_ENABLED", "true"
             buildConfigField "boolean", "RELAYINVITE_SUPPORTED", "true"
             buildConfigField "String", "VARIANT_NAME", "\"Dev/Debug\""
+			buildConfigField "boolean", "REPORT_LOCKS", "true"
         }
 
         xw4dNoSMS {

xwords4/android/app/src/main/java/org/eehouse/android/xw4/BoardDelegate.java

@@ -510,6 +510,7 @@ public class BoardDelegate extends DelegateBase
         m_activity = delegator.getActivity();
     }
 
+    private static int s_noLockCount = 0; // supports a quick debugging hack
     protected void init( Bundle savedInstanceState )
     {
         m_isFirstLaunch = null == savedInstanceState;
@@ -544,7 +545,13 @@ public class BoardDelegate extends DelegateBase
                 public void gotLock( GameLock lock ) {
                     if ( null == lock ) {
                         finish();
+                        if ( BuildConfig.REPORT_LOCKS && ++s_noLockCount == 3 ) {
+                            String msg = "BoardDelegate unable to get lock; holder stack: "
+                                + GameLock.getHolderStack( m_rowid );
+                            CrashTrack.logAndSend( msg );
+                        }
                     } else {
+                        s_noLockCount = 0;
                         m_jniThreadRef = JNIThread.getRetained( lock );
 
                         // see http://stackoverflow.com/questions/680180/where-to-stop- \

xwords4/android/app/src/main/java/org/eehouse/android/xw4/GameLock.java

@@ -64,7 +64,6 @@ public class GameLock implements AutoCloseable, Serializable {
         Owner()
         {
             mThread = Thread.currentThread();
-            // mTrace = mThread.getStackTrace();
             mTrace = android.util.Log.getStackTraceString(new Exception());
         }
 
@@ -361,6 +360,13 @@ public class GameLock implements AutoCloseable, Serializable {
             } ).start();
     }
 
+    public static String getHolderStack( long rowid )
+    {
+        GameLockState state = getFor( rowid );
+        Owner owner = state.mOwners.peek();
+        return owner.mTrace;
+    }
+
     // used only for asserts
     public boolean canWrite()
     {

xwords4/android/app/src/xw4/java/org/eehouse/android/xw4/CrashTrack.java

@@ -24,4 +24,5 @@ import android.content.Context;
 
 public class CrashTrack {
     public static void init( Context context ) {} // does nothing here
+    public static void logAndSend( String msg ) {}
 }

xwords4/android/app/src/xw4d/java/org/eehouse/android/xw4/CrashTrack.java

@@ -60,4 +60,19 @@ public class CrashTrack {
             }
         }
     }
+
+    public static void logAndSend( String msg )
+    {
+        Crashlytics.log( msg );
+        new Thread( new Runnable() {
+                @Override
+                public void run() {
+                    String foo = null;
+                    try {
+                        Thread.sleep( 5000 );
+                        throw new RuntimeException( "crash generator" );
+                    } catch ( InterruptedException ex ) {}
+                }
+            } ).start();
+    }
 }