message: [XLA] Add more tests to ShapeUtil::CommonFactors with degenerated dimensions.
  The comment of ShapeUtil::CommonFactors was ambiguous on the
  behavior of degenerated dimensions. This test serves as documents to
  that (although I think the behavior can be improved).
diff: @@ -76,10 +76,23 @@ TEST(UtilTest, CommonFactors) {
  {/*.a =*/{2, 5, 1, 3},
  /*.b =*/{1, 10, 3, 1},
  /*.expected =*/{{0, 0}, {0, 1}, {2, 2}, {3, 2}, {4, 3}, {4, 4}}},
  - };
  + {/*.a =*/{1, 1, 3},
  + /*.b =*/{1, 1, 3},
  + /*.expected =*/{{0, 0}, {1, 1}, {2, 2}, {3, 3}}},
  + // Splitting and combining dimensions.
  + {/*.a =*/{2, 6},
  + /*.b =*/{4, 3},
  + /*.expected =*/{{0, 0}, {2, 2}}},
  + {/*.a =*/{1, 2, 6},
  + /*.b =*/{4, 1, 3, 1},
  + /*.expected =*/{{0, 0}, {1, 0}, {3, 3}, {3, 4}}},
  + // Extra degenerated dimension (second and third dims in the output) forms
  + // single common factor group.
  + {/*.a =*/{1, 2, 1},
  + /*.b =*/{1, 1, 1, 2},
  + /*.expected =*/{{0, 0}, {1, 1}, {1, 2}, {1, 3}, {2, 4}, {3, 4}}}};
  for (const auto& test_case : test_cases) {
  - EXPECT_TRUE(absl::c_equal(test_case.expected,
  - CommonFactors(test_case.a, test_case.b)));
  + EXPECT_EQ(test_case.expected, CommonFactors(test_case.a, test_case.b));
  }
  }
  