Fixed an issue where tracing events got incorrectly enabled.

base/trace_event/trace_config_unittest.cc

Index: base/trace_event/trace_config_unittest.cc
diff --git a/base/trace_event/trace_config_unittest.cc b/base/trace_event/trace_config_unittest.cc
index 84da739b5477377472c12fa6d0b52b5bd88fc466..1d888912a93b8370edfd91f6a32e266b0fef7d5b 100644
--- a/base/trace_event/trace_config_unittest.cc
+++ b/base/trace_event/trace_config_unittest.cc
@@ -448,6 +448,12 @@ TEST(TraceConfigTest, IsCategoryGroupEnabled) {
   EXPECT_TRUE(tc.IsCategoryGroupEnabled("disabled-by-default-cc"));
   EXPECT_TRUE(tc.IsCategoryGroupEnabled("included"));
   EXPECT_FALSE(tc.IsCategoryGroupEnabled("other_included"));
+
+  // Excluding categories won't enable disabled-by-default ones with the
+  // excluded category is also present in the group.
+  tc = TraceConfig("-excluded", "");
+  EXPECT_STREQ("-excluded", tc.ToCategoryFilterString().c_str());
+  EXPECT_FALSE(tc.IsCategoryGroupEnabled("excluded,disabled-by-default-cc"));
 }
 
 TEST(TraceConfigTest, IsEmptyOrContainsLeadingOrTrailingWhitespace) {