Implement sampling profiler (chromium side change)

content/browser/tracing/tracing_controller_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/tracing/tracing_controller_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/file_util.h"
 #include "base/json/string_escape.h"
@@ skipping 62 matching lines @@
     LOG(ERROR) << "Failed to open " << path_.value();
     return;
   }
   const char* preamble = "{\"traceEvents\": [";
   size_t written = fwrite(preamble, strlen(preamble), 1, file_);
   DCHECK(written == 1);
 }
 
 void TracingControllerImpl::ResultFile::WriteTask(
     const scoped_refptr<base::RefCountedString>& events_str_ptr) {
-  if (!file_)
+  if (!file_ || !events_str_ptr->data().size())
     return;
 
   // If there is already a result in the file, then put a commma
   // before the next batch of results.
   if (has_at_least_one_result_) {
     size_t written = fwrite(",", 1, 1, file_);
     DCHECK(written == 1);
   }
   has_at_least_one_result_ = true;
   size_t written = fwrite(events_str_ptr->data().c_str(),
@@ skipping 322 matching lines @@
                    base::Unretained(this),
                    make_scoped_refptr(trace_message_filter)));
     return;
   }
 
   trace_message_filters_.insert(trace_message_filter);
   if (can_cancel_watch_event()) {
     trace_message_filter->SendSetWatchEvent(watch_category_name_,
                                             watch_event_name_);
   }
-  if (can_disable_recording()) {
+  if (can_disable_recording() || can_disable_monitoring()) {
     trace_message_filter->SendBeginTracing(
         TraceLog::GetInstance()->GetCurrentCategoryFilter().ToString(),
         TraceLog::GetInstance()->trace_options());
   }
 }
 
 void TracingControllerImpl::RemoveTraceMessageFilter(
     TraceMessageFilter* trace_message_filter) {
   if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
     BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
@@ skipping 201 matching lines @@
         base::Bind(&TracingControllerImpl::OnWatchEventMatched,
                    base::Unretained(this)));
     return;
   }
 
   if (!watch_event_callback_.is_null())
     watch_event_callback_.Run();
 }
 
 }  // namespace content