Tracing: make filtering logic more intuitive for multiple categories

This changes the way category filter processes multi-categories groups.
Previously, adding a disabled-by-default- category to a regular category
would prevent the event from matching filter if only regular category
is enabled. This is somewhat counter-intuitive, the expected behavior
is that each category is processed by the filter independently. The new
logic is:

1. if at least one category in event category group matches at
least one category enabled in the filter, the event passes;

2. if at least one category in event category group matches at least
one category explicitly excluded in the filter, the event is
filtered out;

3. the event is passed by default, if included categories list is empty
and event has at least one category that is not disabled-by-default-.

Note no existing tests were modified (though I'm not sure if (2) should
be the way it is).

BUG=

Review URL: https://codereview.chromium.org/788243003

Cr-Commit-Position: refs/heads/master@{#308136}

1 files changed, 16 insertions, 0 deletions

diff --git a/base/debug/trace_event_unittest.cc b/base/debug/trace_event_unittest.cc
index 0904954..85cf4eb 100644
--- a/base/debug/trace_event_unittest.cc
+++ b/base/debug/trace_event_unittest.cc
@@ -1615,6 +1615,22 @@ TEST_F(TraceEventTestFixture, DisabledCategories) {
     EXPECT_FIND_("disabled-by-default-cc");
     EXPECT_FIND_("other_included");
   }
+
+  Clear();
+
+  BeginSpecificTrace("other_included");
+  TRACE_EVENT_INSTANT0(TRACE_DISABLED_BY_DEFAULT("cc") ",other_included",
+                       "first", TRACE_EVENT_SCOPE_THREAD);
+  TRACE_EVENT_INSTANT0("other_included," TRACE_DISABLED_BY_DEFAULT("cc"),
+                       "second", TRACE_EVENT_SCOPE_THREAD);
+  EndTraceAndFlush();
+
+  {
+    const DictionaryValue* item = NULL;
+    ListValue& trace_parsed = trace_parsed_;
+    EXPECT_FIND_("disabled-by-default-cc,other_included");
+    EXPECT_FIND_("other_included,disabled-by-default-cc");
+  }
 }
 
 TEST_F(TraceEventTestFixture, NormallyNoDeepCopy) {