Add a PrintTo function for rtc::Optional to aid with testing.

webrtc/base/optional.cc

Index: webrtc/base/optional.cc
diff --git a/webrtc/base/optional.cc b/webrtc/base/optional.cc
index 6bebdd5a19225fcf46424e97c95d28ccba1b800e..455cfe939a936f9e2f0571d2a5624b42f42f7e55 100644
--- a/webrtc/base/optional.cc
+++ b/webrtc/base/optional.cc
@@ -10,6 +10,8 @@
 
 #include "webrtc/base/optional.h"
 
+#include <iomanip>
+
 namespace rtc {
 namespace optional_internal {
 
@@ -19,5 +21,18 @@ void* FunctionThatDoesNothingImpl(void* x) { return x; }
 
 #endif
 
+void OptionalPrintObjectBytes(const unsigned char* bytes,
+                              size_t size,
+                              std::ostream* os) {
+  *os << "<optional with " << size << "-byte object [";
+  for (size_t i = 0; i != size; ++i) {
+    *os << (i == 0 ? "" : ((i & 1) ? "-" : " "));
+    *os << std::hex << std::setw(2) << std::setfill('0')
+        << static_cast<int>(bytes[i]);
+  }
+  *os << "]>";
+}

[kwiberg-webrtc, 2017/02/17 13:51:22]

This is just for testing, so you should probably inline it (making tests bigger,
but production binaries smaller).

[ossu, 2017/02/17 14:02:19]

I'd rather keep this cruft as isolated as possible. It's only <iomanip> but it'd
be nice to avoid including that in everything that uses Optional, if possible. I
don't think the size increase is noticeable.

[tommi, 2017/02/17 14:08:55]

My concern is that if we get to the point that we can do builds that are free of
iostream, then just one place that pulls it in, will be enough to make a
significant difference.  If the argument is "it's just a drop in the ocean",
then the counter argument is "death by a thousand cuts" :)

Logging is very costly as it is, so we have our work cut out to address that and
there are indeed situations where we've had to throw out all logging in order to
be able to reach performance targets.
If we add more things to battle, then we make the battle harder for ourselves in
the end.
So, whatever we can do to make utilities like these unavailable to production
code, are appreciated. (if we could do what Karl suggests, make testing easier
while making production code smaller, then that would be great)

+
 }  // namespace optional_internal
+
 }  // namespace rtc