Adding shutdown tracing capabilities

content/browser/browser_shutdown_profile_dumper.cc

+// Copyright (c) 2012 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/browser_shutdown_profile_dumper.h"
+
+#include "base/base_switches.h"
+#include "base/command_line.h"
+#include "base/debug/trace_event.h"
+#include "base/debug/trace_event_impl.h"
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "content/public/common/content_switches.h"
+
+namespace content {
+
+BrowserShutdownProfileDumper::BrowserShutdownProfileDumper()
+    : blocks_(0),
+      dump_file_(0) {
+}
+
+BrowserShutdownProfileDumper::~BrowserShutdownProfileDumper() {
+  WriteTracesToDisc(GetFileName());
+}
+
+void BrowserShutdownProfileDumper::WriteTracesToDisc(base::FilePath file_name) {
+  // Note: I have seen a usage of 0.000xx% when dumping - which fits easily.
+  // Since the tracer stops when the trace buffer is filled, we'd rather save
+  // what we have then nothing since we might see from the amount of events
+  // who caused the problem.
+  VLOG(1) << "Flushing shutdown traces to disc. The buffer is %" <<
+      base::debug::TraceLog::GetInstance()->GetBufferPercentFull() <<
+      " full.";
+  DCHECK(!dump_file_);
+  dump_file_ = file_util::OpenFile(file_name, "w+");
+  if (!IsFileValid()) {
+    LOG(ERROR) << "Failed to open performance trace file: " <<
+        file_name.value();
+    return;
+  }
+  WriteString("{\"traceEvents\":");
+  WriteString("[");
+
+  base::debug::TraceLog::GetInstance()->Flush(
+      base::Bind(&BrowserShutdownProfileDumper::WriteTraceDataCollected,
+      base::Unretained(this)));
+
+  WriteString("]");
+  WriteString("}");
+  CloseFile();
+}
+
+base::FilePath BrowserShutdownProfileDumper::GetFileName() {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  base::FilePath trace_file =
+      command_line.GetSwitchValuePath(switches::kTraceShutdownFile);
+
+  if (!trace_file.empty())
+    return trace_file;
+
+  // Default to saving the startup trace into the current dir.
+  return base::FilePath().AppendASCII("chrometrace.log");
+}
+
+void BrowserShutdownProfileDumper::WriteTraceDataCollected(
+    const scoped_refptr<base::RefCountedString>& events_str) {
+  if (!IsFileValid())
+    return;
+  if (blocks_) {
+    // Blocks are not comma separated. Beginning with the second block we
+    // start therefore to add one in front of the previous block.
+    WriteString(",");
+  }
+  blocks_++;

[DaveMoore, 2013/09/03 17:02:48]

Nit: ++blocks_;

[Mr4D (OOO till 08-26), 2013/09/03 17:34:34]

Done.

+  WriteString(events_str->data());

[DaveMoore, 2013/09/03 17:02:48]

What you're doing currently is taking the char* return from data() which may not
be terminated and calling WriteString() which creates a new std::string() out of
that data (potentially walking off the end) which then calls WriteChars() with
the char* data. 

Instead you should just call WriteString() with events_str.

[Mr4D (OOO till 08-26), 2013/09/03 17:34:34]

Actually... RefCountedString does return it's std::string - not a char*. As such
the length as well as the string should be properly handled.

[DaveMoore, 2013/09/03 20:24:11]

You are right.
On 2013/09/03 17:34:34, Mr4D wrote:

+}
+
+bool BrowserShutdownProfileDumper::IsFileValid() {
+  return dump_file_ && (ferror(dump_file_) == 0);
+}
+
+void BrowserShutdownProfileDumper::WriteString(const std::string& string) {
+  WriteChars(string.data(), string.size());
+}
+
+void BrowserShutdownProfileDumper::WriteChars(const char* chars, size_t size) {
+  if (!IsFileValid())
+    return;
+
+  size_t written = fwrite(chars, 1, size, dump_file_);
+  if (written != size) {
+    LOG(ERROR) << "Error " << ferror(dump_file_) <<
+        " in fwrite() to trace file";
+    CloseFile();
+  }
+}
+
+void BrowserShutdownProfileDumper::CloseFile() {
+  if (!IsFileValid())
+    return;
+  file_util::CloseFile(dump_file_);
+  dump_file_ = 0;
+}
+
+}  // namespace content