[Interpreter] List top dispatch sources and destinations for a given Ignition bytecode.

tools/ignition/bytecode_dispatches_report_test.py

Index: tools/ignition/bytecode_dispatches_report_test.py
diff --git a/tools/ignition/bytecode_dispatches_report_test.py b/tools/ignition/bytecode_dispatches_report_test.py
index 21aa675db3e0ea856d42730f30036082bdd9dfdc..523dac2960d8da5e0d2ca9f31288e6201a80b041 100644
--- a/tools/ignition/bytecode_dispatches_report_test.py
+++ b/tools/ignition/bytecode_dispatches_report_test.py
@@ -41,3 +41,14 @@ class BytecodeDispatchesReportTest(unittest.TestCase):
       ('a',  25),
       ('b',   5)
     ])
+
+  def test_find_top_dispatch_sources(self):
+    top_dispatch_sources = bdr.find_top_dispatch_sources({
+      "a": {"a": 10, "b":  8, "c":  7},
+      "b": {"a":  1, "c":  4},
+      "c": {"a": 42, "b": 12, "c": 99}
+    }, "b", 10)
+    self.assertListEqual(top_dispatch_sources, [
+      ("c", 12),
+      ("a",  8)
+    ])