Implement serial API for Windows.

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 0b689621df4b03bd93fa9c20488a62c73245fd0a..ab2716317cbb425a63f4ab2d3d1874f5377893ea 100644
--- a/base/platform_file_win.cc
+++ b/base/platform_file_win.cc
@@ -134,8 +134,12 @@ int ReadPlatformFile(PlatformFile file, int64 offset, char* data, int size) {
   return -1;
 }
 
-int ReadPlatformFileNoBestEffort(PlatformFile file, int64 offset,
-                                 char* data, int size) {
+int ReadPlatformFileAtCurrentPos(PlatformFile file, char* data, int size) {
+  return ReadPlatformFile(file, 0, data, size);
+}
+
+int ReadPlatformFileNoBestEffort(PlatformFile file, int64 offset, char* data,
+                                 int size) {
   return ReadPlatformFile(file, offset, data, size);
 }
 
@@ -159,6 +163,11 @@ int WritePlatformFile(PlatformFile file, int64 offset,
   return -1;
 }
 
+int WritePlatformFileAtCurrentPos(PlatformFile file, const char* data,
+                                  int size) {
+  return WritePlatformFile(file, 0, data, size);
+}
+
 bool TruncatePlatformFile(PlatformFile file, int64 length) {
   base::ThreadRestrictions::AssertIOAllowed();
   if (file == kInvalidPlatformFileValue)