Add an "append flag" to base::PlatformFile.

base/platform_file_posix.cc

Index: base/platform_file_posix.cc
diff --git a/base/platform_file_posix.cc b/base/platform_file_posix.cc
index beae804c629c86a6b8fa4ef716f601552d9a114e..a8be8a4a95ec4351c824f1fece257a00af033dfc 100644
--- a/base/platform_file_posix.cc
+++ b/base/platform_file_posix.cc
@@ -81,6 +81,7 @@ PlatformFile CreatePlatformFileUnsafe(const FilePath& name,
     open_flags |= O_WRONLY;
   } else if (!(flags & PLATFORM_FILE_READ) &&
              !(flags & PLATFORM_FILE_WRITE_ATTRIBUTES) &&
+             !(flags & PLATFORM_FILE_APPEND) &&
              !(flags & PLATFORM_FILE_OPEN_ALWAYS)) {
     NOTREACHED();
   }
@@ -88,6 +89,11 @@ PlatformFile CreatePlatformFileUnsafe(const FilePath& name,
   if (flags & PLATFORM_FILE_TERMINAL_DEVICE)
     open_flags |= O_NOCTTY | O_NDELAY;
 
+  if (flags & PLATFORM_FILE_APPEND && flags & PLATFORM_FILE_READ)
+    open_flags |= O_APPEND | O_RDWR;
+  else if (flags & PLATFORM_FILE_APPEND)

[jar (doing other things), 2013/06/04 23:31:50]

nit: I guess you shouldn't change this... as it is pervasively done throughout
this file..... but I didn't like having to read the pattern of:

if (a && b)
 do_one_thing();
else if (a)  // Note re-use of a test, hopefully spelled the same :-/
  do_something_else();

and would vastly prefer:
if (a) {
  if (b)
    do_one_thing()
  else
    do_something else
}


If by any chance you too are bothered by this... you could consider renovating
this... but I can't justify insistence... and it is probably best to leave this
as is... and copy the style as you have done <sigh>.

+    open_flags |= O_APPEND | O_WRONLY;
+
   COMPILE_ASSERT(O_RDONLY == 0, O_RDONLY_must_equal_zero);
 
   int mode = S_IRUSR | S_IWUSR;