Add granular file tracing.

base/files/file.cc

Index: base/files/file.cc
diff --git a/base/files/file.cc b/base/files/file.cc
index 4c0e5ded47c90d000a7fb6e80ff1e5a160445743..8b8720c0f558936d5079e33b49ca6717db89e7a7 100644
--- a/base/files/file.cc
+++ b/base/files/file.cc
@@ -6,6 +6,7 @@
 #include "base/files/file_path.h"
 #include "base/metrics/histogram.h"
 #include "base/timer/elapsed_timer.h"
+#include "base/trace_event/trace_event.h"
 
 #if defined(OS_POSIX)
 #include "base/files/file_posix_hooks_internal.h"
@@ -29,11 +30,11 @@ File::File()
 }
 
 #if !defined(OS_NACL)
-File::File(const FilePath& name, uint32 flags)
+File::File(const FilePath& path, uint32 flags)
     : error_details_(FILE_OK),
       created_(false),
       async_(false) {
-  Initialize(name, flags);
+  Initialize(path, flags);
 }
 #endif
 
@@ -57,18 +58,21 @@ File::File(Error error_details)
 
 File::File(RValue other)
     : file_(other.object->TakePlatformFile()),
+      path_(other.object->path_),
       error_details_(other.object->error_details()),
       created_(other.object->created()),
       async_(other.object->async_) {
 #if defined(OS_POSIX)
-   if (IsValid())
-     ProtectFileDescriptor(GetPlatformFile());
+  if (IsValid())
+    ProtectFileDescriptor(GetPlatformFile());
 #endif
 }
 
 File::~File() {
   // Go through the AssertIOAllowed logic.
   Close();
+  TRACE_EVENT_ASYNC_END1(kTraceGroup, "File", this,

[Lei Zhang, 2015/04/27 22:55:55]

We may not always call TRACE_EVENT_ASYNC_BEGIN1() in Initialize(), would that
mismatch cause trouble here?

[Dan Beam, 2015/04/28 03:17:11]

not sure but just made this TRACE_EVENT_ASYNC_{BEGIN/END}0 instead and just
passing |this| (omitting path_)

+                         "path", path_.AsUTF8Unsafe());

[Dan Beam, 2015/04/24 22:27:02]

should I be passing along the path here?

 }
 
 File& File::operator=(RValue other) {
@@ -83,12 +87,15 @@ File& File::operator=(RValue other) {
 }
 
 #if !defined(OS_NACL)
-void File::Initialize(const FilePath& name, uint32 flags) {
-  if (name.ReferencesParent()) {
+void File::Initialize(const FilePath& path, uint32 flags) {
+  path_ = path;
+  if (path_.ReferencesParent()) {
     error_details_ = FILE_ERROR_ACCESS_DENIED;
     return;
   }
-  DoInitialize(name, flags);
+  TRACE_EVENT_ASYNC_BEGIN1(kTraceGroup, "File", this,
+                           "path", path_.AsUTF8Unsafe());
+  DoInitialize(flags);
 }
 #endif
 
@@ -136,6 +143,9 @@ std::string File::ErrorToString(Error error) {
   return "";
 }
 
+// static
+const char File::kTraceGroup[] = TRACE_DISABLED_BY_DEFAULT("file");
+
 bool File::Flush() {
   ElapsedTimer timer;
   bool return_value = DoFlush();