Add granular file tracing.

base/files/file.h

Index: base/files/file.h
diff --git a/base/files/file.h b/base/files/file.h
index 89077b41c1d8d03a9aa1e33ea822b9fb9454f807..55595804be6e6891fadeb8ff311d29a84f80932f 100644
--- a/base/files/file.h
+++ b/base/files/file.h
@@ -18,6 +18,7 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/files/file_path.h"
 #include "base/files/scoped_file.h"
 #include "base/gtest_prod_util.h"
 #include "base/move.h"
@@ -31,8 +32,6 @@ FORWARD_DECLARE_TEST(FileTest, MemoryCorruption);
 
 namespace base {
 
-class FilePath;
-
 #if defined(OS_WIN)
 typedef HANDLE PlatformFile;
 #elif defined(OS_POSIX)
@@ -162,8 +161,8 @@ class BASE_EXPORT File {
   File();
 
   // Creates or opens the given file. This will fail with 'access denied' if the
-  // |name| contains path traversal ('..') components.
-  File(const FilePath& name, uint32 flags);
+  // |path| contains path traversal ('..') components.
+  File(const FilePath& path, uint32 flags);
 
   // Takes ownership of |platform_file|.
   explicit File(PlatformFile platform_file);
@@ -180,7 +179,7 @@ class BASE_EXPORT File {
   File& operator=(RValue other);
 
   // Creates or opens the given file.
-  void Initialize(const FilePath& name, uint32 flags);
+  void Initialize(const FilePath& path, uint32 flags);
 
   bool IsValid() const;
 
@@ -191,7 +190,7 @@ class BASE_EXPORT File {
 
   // Returns the OS result of opening this file. Note that the way to verify
   // the success of the operation is to use IsValid(), not this method:
-  //   File file(name, flags);
+  //   File file(path, flags);
   //   if (!file.IsValid())
   //     return;
   Error error_details() const { return error_details_; }
@@ -305,6 +304,9 @@ class BASE_EXPORT File {
  private:
   FRIEND_TEST_ALL_PREFIXES(::FileTest, MemoryCorruption);
 
+  // The tracing group file traces will show up as.
+  static const char kTraceGroup[];
+
 #if defined(OS_POSIX)
   // Encloses a single ScopedFD, saving a cheap tamper resistent memory checksum
   // alongside it. This checksum is validated at every access, allowing early
@@ -350,9 +352,9 @@ class BASE_EXPORT File {
   };
 #endif
 
-  // Creates or opens the given file. Only called if |name| has no traversal
+  // Creates or opens the given file. Only called if |path_| has no traversal
   // ('..') components.
-  void DoInitialize(const FilePath& name, uint32 flags);
+  void DoInitialize(uint32 flags);
 
   // TODO(tnagel): Reintegrate into Flush() once histogram isn't needed anymore,
   // cf. issue 473337.
@@ -366,6 +368,9 @@ class BASE_EXPORT File {
   MemoryCheckingScopedFD file_;
 #endif
 
+  // Path that |Initialize()| was called with. Can be unsafe (e.g. have '..').
+  FilePath path_;
+
   Error error_details_;
   bool created_;
   bool async_;