Change memory dumps to not use periodic dumps by default.

content/browser/tracing/tracing_ui.cc

Index: content/browser/tracing/tracing_ui.cc
diff --git a/content/browser/tracing/tracing_ui.cc b/content/browser/tracing/tracing_ui.cc
index 14389658a420ecb7b3f5d00d287fedeabee87753..d455be3d53d1af6b2ae33d2ef4fa7242798c74d9 100644
--- a/content/browser/tracing/tracing_ui.cc
+++ b/content/browser/tracing/tracing_ui.cc
@@ -89,6 +89,22 @@ bool GetTracingOptions(const std::string& data64,
   *trace_config = base::trace_event::TraceConfig(category_filter_string,
                                                  record_mode);
 
+  // When enabling memory-infra via tracing, use periodic dumping to trigger a
+  // detailed dump every 5s.
+  if (category_filter_string.find(
+          base::trace_event::MemoryDumpManager::kTraceCategory) !=

[Primiano Tucci (use gerrit), 2017/05/26 19:12:33]

Iirc there is a iscategoryenabled in traceconfig that makes this a bit cleaner. 
The real bug here is that I think somebody created a memory-infra.V8 which adds
some extra expensive stuff. This string matching will get also that. Is category
enabled() will not. 

[erikchen, 2017/05/26 20:31:13]

Done.

+      std::string::npos) {
+    base::trace_event::TraceConfig::MemoryDumpConfig::Trigger trigger = {
+        5000,  // min_time_between_dumps_ms
+        base::trace_event::MemoryDumpLevelOfDetail::DETAILED,
+        base::trace_event::MemoryDumpType::PERIODIC_INTERVAL};
+    base::trace_event::TraceConfig::MemoryDumpConfig memory_dump_config;
+    memory_dump_config.triggers.push_back(trigger);
+    memory_dump_config.allowed_dump_modes.insert(
+        base::trace_event::MemoryDumpLevelOfDetail::DETAILED);

[Primiano Tucci (use gerrit), 2017/05/26 19:12:33]

Check with ssid, I don't think you need this. This should be only for
restricting, this one here should be the default behavior. 

[erikchen, 2017/05/26 20:31:13]

This is necessary, because a freshly constructed MemoryDumpConfig doesn't pick
up the default behavior. *shrug*. You're welcome to fix this. :)

[ssid, 2017/05/26 21:56:07]

Yeah we only thought about the trace config string case where if it is not
specified then all modes are assumed. While constructing the object itself, we
need to add modes manually. meh this is unfortunate. add a todo for me.

[erikchen, 2017/05/27 00:51:03]

Done.

+    trace_config->ResetMemoryDumpConfig(memory_dump_config);
+  }
+
   bool enable_systrace;
   options_ok &= options->GetBoolean("useSystemTracing", &enable_systrace);
   if (enable_systrace)