Pepper: Add append support to FileIO.

ppapi/tests/test_file_io.cc

Index: ppapi/tests/test_file_io.cc
diff --git a/ppapi/tests/test_file_io.cc b/ppapi/tests/test_file_io.cc
index 50064192a43ca97e10d0031b01fe1b1327c10a6c..2d0da5c11994e95a7a43d6c8f2baadbfc8002174 100644
--- a/ppapi/tests/test_file_io.cc
+++ b/ppapi/tests/test_file_io.cc
@@ -6,6 +6,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -414,6 +415,22 @@ std::string TestFileIO::TestReadWriteSetLength() {
   ASSERT_EQ(PP_OK, rv);
   ASSERT_EQ(std::string("testtest\0\0\0\0", 12), read_buffer);
 
+  // Append to the end of the file.
+  pp::FileIO file_io2(instance_);
+  callback.WaitForResult(file_io2.Open(file_ref,
+                                       PP_FILEOPENFLAG_CREATE |
+                                       PP_FILEOPENFLAG_READ |
+                                       PP_FILEOPENFLAG_APPEND,
+                                       callback.GetCallback()));
+  rv = WriteEntireBuffer(instance_->pp_instance(), &file_io2, 0, "appended",
+                         callback_type());
+  ASSERT_EQ(PP_OK, rv);
+  read_buffer.clear();
+  rv = ReadEntireFile(instance_->pp_instance(), &file_io2, 0, &read_buffer,
+                      callback_type());
+  ASSERT_EQ(PP_OK, rv);
+  ASSERT_EQ(std::string("testtesttest\0\0\0\0appended", 24), read_buffer);
+
   PASS();
 }