[Interpreter] Report hottest bytecodes in bytecode_dispatches_report.py

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 c31bb862cba88d59b63958927dce25f17174bcd4..ee76a4aac7c14637959568d99bcbb58e049c21de 100644
--- a/tools/ignition/bytecode_dispatches_report_test.py
+++ b/tools/ignition/bytecode_dispatches_report_test.py
@@ -29,3 +29,10 @@ class BytecodeDispatchesReportTest(unittest.TestCase):
                                          [10,  8,  7]]).all())
     self.assertListEqual(xlabels, ['a', 'b', 'c'])
     self.assertListEqual(ylabels, ['c', 'b', 'a'])
+
+  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}}, 2)
+    self.assertListEqual(top_dispatch_sources, [('c', 153), ('a', 25)])