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

base/platform_file_win.cc

Index: base/platform_file_win.cc
diff --git a/base/platform_file_win.cc b/base/platform_file_win.cc
index cdc06bd1ca2bd192f150d89316d24f5348c5eb05..98721705fe3a1b4ca5f9e096dbee14f556a16a27 100644
--- a/base/platform_file_win.cc
+++ b/base/platform_file_win.cc
@@ -58,6 +58,11 @@ PlatformFile CreatePlatformFileUnsafe(const FilePath& name,
     access |= FILE_WRITE_ATTRIBUTES;
   if (flags & PLATFORM_FILE_EXECUTE)
     access |= GENERIC_EXECUTE;
+  if (flags & PLATFORM_FILE_APPEND) {
+    access |= FILE_APPEND_DATA;
+    if (flags & PLATFORM_FILE_WRITE)  // Invalid.

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

Note that the corresponding check on CREATE vs OPEN was done with a DCHECK
(lines 29, 34, etc.).  You should probably follow that pattern:
DCHECK_FALSE(flags & PLATFORM_FILE_WRITE);

+      return NULL;
+  }
 
   DWORD sharing = (flags & PLATFORM_FILE_EXCLUSIVE_READ) ? 0 : FILE_SHARE_READ;
   if (!(flags & PLATFORM_FILE_EXCLUSIVE_WRITE))