[Turbofan] Fixing A/B/C test operators in unittests

Currently only A test operators had output, but since ABReducer and BCReducer
perform in-place replacement of A nodes into B nodes, and then sometimes into
C nodes, we need B and C nodes to have as many outputs. Otherwise, we run into
a situation where a node {x} has a use {y}, but its operators has 0 outputs,
which is inconsistent.

Bug: 
Change-Id: I0f73b83d2115dfeda3c9cbc97b9a2fc168f4c31b
Reviewed-on: https://chromium-review.googlesource.com/603716Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Alexandre Talon <alexandret@google.com>
Cr-Commit-Position: refs/heads/master@{#47202}

test/unittests/compiler/graph-reducer-unittest.cc

@@ -45,12 +45,12 @@ const uint8_t kOpcodeC2 = 32;
 static TestOperator kOpA0(kOpcodeA0, Operator::kNoWrite, "opa1", 0, 1);
 static TestOperator kOpA1(kOpcodeA1, Operator::kNoProperties, "opa2", 1, 1);
 static TestOperator kOpA2(kOpcodeA2, Operator::kNoProperties, "opa3", 2, 1);
-static TestOperator kOpB0(kOpcodeB0, Operator::kNoWrite, "opa0", 0, 0);
-static TestOperator kOpB1(kOpcodeB1, Operator::kNoWrite, "opa1", 1, 0);
-static TestOperator kOpB2(kOpcodeB2, Operator::kNoWrite, "opa2", 2, 0);
-static TestOperator kOpC0(kOpcodeC0, Operator::kNoWrite, "opc0", 0, 0);
-static TestOperator kOpC1(kOpcodeC1, Operator::kNoWrite, "opc1", 1, 0);
-static TestOperator kOpC2(kOpcodeC2, Operator::kNoWrite, "opc2", 2, 0);
+static TestOperator kOpB0(kOpcodeB0, Operator::kNoWrite, "opb0", 0, 1);
+static TestOperator kOpB1(kOpcodeB1, Operator::kNoWrite, "opb1", 1, 1);
+static TestOperator kOpB2(kOpcodeB2, Operator::kNoWrite, "opb2", 2, 1);
+static TestOperator kOpC0(kOpcodeC0, Operator::kNoWrite, "opc0", 0, 1);
+static TestOperator kOpC1(kOpcodeC1, Operator::kNoWrite, "opc1", 1, 1);
+static TestOperator kOpC2(kOpcodeC2, Operator::kNoWrite, "opc2", 2, 1);
 
 struct MockReducer : public Reducer {
   MOCK_CONST_METHOD0(reducer_name, const char*());