Debugging tests: fix breakpoint setup when line table is empty

When we set a breakpoint on the first line of a method, we request
its line table then select the first line in this table and set the
breakpoint on the corresponding instruction index.

If a method has no line table (which is the case for synthesized
methods), then we just need to set the breakpoint on the first
instruction.

Change-Id: I9d00f06d22bc5f2c604d41199710c569662f7c53
diff --git a/src/test/java/com/android/tools/r8/debug/DebugTestBase.java b/src/test/java/com/android/tools/r8/debug/DebugTestBase.java
index 685e8f7..f65e204 100644
--- a/src/test/java/com/android/tools/r8/debug/DebugTestBase.java
+++ b/src/test/java/com/android/tools/r8/debug/DebugTestBase.java
@@ -1482,10 +1482,16 @@
       ReplyPacket replyPacket = getMirror().getLineTable(classId, breakpointMethodId);
       checkReplyPacket(replyPacket, "Failed to get method line table");
       long start = replyPacket.getNextValueAsLong(); // start
-      long end = replyPacket.getNextValueAsLong(); // end
+      replyPacket.getNextValueAsLong(); // end
       int linesCount = replyPacket.getNextValueAsInt();
       if (linesCount == 0) {
-        pcs.add(-1L);
+        if (lineToSearch == FIRST_LINE) {
+          // There is no line table but we are not looking for a specific line. Therefore just
+          // set the breakpoint on the 1st instruction.
+          pcs.add(start);
+        } else {
+          pcs.add(-1L);
+        }
       } else {
         if (lineToSearch == FIRST_LINE) {
           // Read only the 1st line because code indices are in ascending order