Added a whitelist for trace events that are known to be PII-less.

content/browser/tracing/tracing_controller_impl.cc

Index: content/browser/tracing/tracing_controller_impl.cc
diff --git a/content/browser/tracing/tracing_controller_impl.cc b/content/browser/tracing/tracing_controller_impl.cc
index 3a235fe5bdaf803c7790dfdb12de1e554e952550..4a1a5adab293fda919133e66102b6eb17a29d9b6 100644
--- a/content/browser/tracing/tracing_controller_impl.cc
+++ b/content/browser/tracing/tracing_controller_impl.cc
@@ -13,6 +13,7 @@
 #include "content/browser/tracing/tracing_ui.h"
 #include "content/common/child_process_messages.h"
 #include "content/public/browser/browser_message_filter.h"
+#include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
 
 #if defined(OS_CHROMEOS)
@@ -96,6 +97,11 @@ void TracingControllerImpl::SetEnabledOnFileThread(
 
   TraceLog::GetInstance()->SetEnabled(
       category_filter, static_cast<TraceLog::Mode>(mode), trace_options);
+  if (trace_options.enable_args_whitelist) {
+    TraceLog::GetInstance()->SetEventFilterPredicate(
+        GetContentClient()->GetTraceEventFilterPredicate());

[jam, 2015/05/12 23:16:32]

why do you need to change content?  seems like chrome can call TraceLog
directly?

[oystein (OOO til 10th of July), 2015/05/12 23:25:12]

Tracing is primarily a content/ concept; there's no initialization of tracing
done in chrome/, so I'd have to add some new hook points there. The predicate
also needs to be accessible from content/public/ for the sake of
components/tracing/ anyway, so I'm not sure if setting this from chrome/ gains
us anything?

+  }
+
   BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, callback);
 }