[tracing] Add browser test for background memory tracing

chrome/test/base/tracing.h

Index: chrome/test/base/tracing.h
diff --git a/chrome/test/base/tracing.h b/chrome/test/base/tracing.h
index 38832d822ff2b85907ab6a15d733527cf193a5a4..654f762912ad33996d7947904dd10da51a2b3c97 100644
--- a/chrome/test/base/tracing.h
+++ b/chrome/test/base/tracing.h
@@ -9,28 +9,30 @@
 
 #include "base/compiler_specific.h"
 #include "base/time/time.h"
+#include "base/trace_event/trace_config.h"
 
 namespace tracing {
 
 // Called from UI thread.
 // Begin tracing specified category_patterns on the browser.
-// |category_patterns| is a comma-delimited list of category wildcards.
-// A category pattern can have an optional '-' prefix to make  categories with
-// matching categorys excluded. Either all category_patterns must be included
-// or all must be excluded.
-//
-// Example: BeginTracing("test_MyTest*");
-// Example: BeginTracing("test_MyTest*,test_OtherStuff");
-// Example: BeginTracing("-excluded_category1,-excluded_category2");
+// |trace_config| specifies the configuration for tracing. This includes the
+// list of categories enabled, tracing modes and memory dumps configuration.
 //
-// See base/trace_event/trace_event.h for documentation of included and excluded
-// category_patterns.
-bool BeginTracing(const std::string& category_patterns) WARN_UNUSED_RESULT;
+// See base/trace_event/trace_config.h for documentation of configurations.
+bool BeginTracing(const base::trace_event::TraceConfig& trace_config)

[Primiano Tucci (use gerrit), 2016/06/15 14:19:57]

If you kept the old version would have required less owners  to review :)
Happy in both cases really.
Consider that below you still have the version with category_patterns, so you
don't have the argument of "for consistency, let's use the new TraceConfig
everywhere", which would have won.
Anyways, happy in both cases, this is a minor thing really.

[ssid, 2016/06/15 17:50:30]

Yeah I wanted to change that one, but too big a change. It makes sense to just
add another function here

+    WARN_UNUSED_RESULT;
 
 // Called from UI thread.
 // Specify a watch event in order to use the WaitForWatchEvent function.
 // After |num_occurrences| of the given event have been seen on a particular
 // process, WaitForWatchEvent will return.
+// |category_patterns| is a comma-delimited list of category wildcards.
+// A category pattern can have an optional '-' prefix to make  categories with
+// matching categorys excluded. Either all category_patterns must be included
+// or all must be excluded.
+//
+// Examples: "test_MyTest*", "test_MyTest*,test_OtherStuff",
+//           "-excluded_category1,-excluded_category2"
 bool BeginTracingWithWatch(const std::string& category_patterns,
                            const std::string& category_name,
                            const std::string& event_name,