Created a blocking copy to temporary file function.

mojo/data_pipe_utils/data_pipe_file_utils.cc

Index: mojo/data_pipe_utils/data_pipe_file_utils.cc
diff --git a/mojo/data_pipe_utils/data_pipe_file_utils.cc b/mojo/data_pipe_utils/data_pipe_file_utils.cc
index e37c8dfe9aeee9140bb33717c5b55d5066c8f9b3..1bba30748d8c541e6a138efef3540c8f3df054ee 100644
--- a/mojo/data_pipe_utils/data_pipe_file_utils.cc
+++ b/mojo/data_pipe_utils/data_pipe_file_utils.cc
@@ -329,6 +329,23 @@ bool BlockingCopyToFile(ScopedDataPipeConsumerHandle source,
                             base::Bind(&CopyToFileHelper, fp.get()));
 }
 
+bool BlockingCopyToTempFile(ScopedDataPipeConsumerHandle source,
+                            FILE** fpp) {

[viettrungluu, 2015/09/01 23:36:25]

Possibly this should be a base::ScopedFILE*.

Or you could return a base::ScopedFILE, with it being null on failure.

[Sean Klein, 2015/09/01 23:57:52]

Out of curiosity, what is the difference between a ScopedFILE and a FILE? I see
the documentation in base which says "Automatically closes |FILE*|s", but it is
not clear to me when this ScopedFILE is actually closed. Would it be when no one
holds a reference to the FILE * anymore?

[jamesr, 2015/09/02 00:06:39]

base::ScopedFILE's destructor calls fclose()

+  base::FilePath path;
+  *fpp = (base::CreateAndOpenTemporaryFile(&path));
+  if (!*fpp) {
+    LOG(ERROR) << "CreateAndOpenTemporaryFile failed in"
+               << "BlockingCopyToTempFile";
+    return false;
+  }
+  if (unlink(path.value().c_str())) {
+    LOG(ERROR) << "Failed to unlink temporary file\n";

[viettrungluu, 2015/09/01 23:36:25]

Also: no \n needed here.
More importantly, it's perhaps a bit unexpected that *fpp gets set even on
failure here.

[Sean Klein, 2015/09/01 23:57:52]

Done.

+    return false;
+  }
+  return BlockingCopyHelper(source.Pass(),
+                            base::Bind(&CopyToFileHelper, *fpp));
+}
+
 void CopyToFile(ScopedDataPipeConsumerHandle source,
                 const base::FilePath& destination,
                 base::TaskRunner* task_runner,