Define ParamTraits<long>::Log() on Fuchsia

Previously the function was declared, but not defined.

Bug: 734791
Change-Id: I848bca19b1e79f33c8f4b796f5b340fdade315f9
Reviewed-on: https://chromium-review.googlesource.com/565796Reviewed-by: Ken Rockot <rockot@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486216}

ipc/ipc_message_utils.cc

@@ -423,7 +423,7 @@ void ParamTraits<unsigned int>::Log(const param_type& p, std::string* l) {
   l->append(base::UintToString(p));
 }
 
-#if defined(OS_WIN) || defined(OS_LINUX) || \
+#if defined(OS_WIN) || defined(OS_LINUX) || defined(OS_FUCHSIA) || \
     (defined(OS_ANDROID) && defined(ARCH_CPU_64_BITS))
 void ParamTraits<long>::Log(const param_type& p, std::string* l) {
   l->append(base::Int64ToString(static_cast<int64_t>(p)));