Fixed category used for JSON exported StackCpuSampling events

This caused slow reports whitelisting to not catch these events.

R=ssid@google.com

Bug:chromium:1046918
Change-Id: Ib4edff57c702cd59c294502297dc8e1efb25fa1f
diff --git a/src/trace_processor/export_json_unittest.cc b/src/trace_processor/export_json_unittest.cc
index ecf9c5c..be4cc90 100644
--- a/src/trace_processor/export_json_unittest.cc
+++ b/src/trace_processor/export_json_unittest.cc
@@ -1402,7 +1402,7 @@
   EXPECT_EQ(event["id"].asString(), "0x1");
   EXPECT_EQ(event["ts"].asInt64(), kTimestamp / 1000);
   EXPECT_EQ(event["tid"].asInt(), static_cast<int>(kThreadID));
-  EXPECT_EQ(event["cat"].asString(), "disabled_by_default-cpu_profiler");
+  EXPECT_EQ(event["cat"].asString(), "disabled-by-default-cpu_profiler");
   EXPECT_EQ(event["name"].asString(), "StackCpuSampling");
   EXPECT_EQ(event["s"].asString(), "t");
   EXPECT_EQ(event["args"]["frames"].asString(),