Make %DebugPrint work correctly on Android

On Android, %DebugPrint should output to the Android log instead of
stdout.

R=mstarzinger@chromium.org

Bug: v8:7820
Change-Id: Ia2ab14f1e4ae15914a1e0e721457f83b288683ff
Reviewed-on: https://chromium-review.googlesource.com/1088691
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53559}

src/runtime/runtime-test.cc

@@ -5,6 +5,7 @@
 #include "src/runtime/runtime-utils.h"
 
 #include <memory>
+#include <sstream>
 
 #include "src/api.h"
 #include "src/arguments.h"
@@ -530,7 +531,7 @@ RUNTIME_FUNCTION(Runtime_DebugPrint) {
   // MaybeObject*.
   MaybeObject* maybe_object = reinterpret_cast<MaybeObject*>(args[0]);
 
-  OFStream os(stdout);
+  std::ostringstream os;
   if (maybe_object->IsClearedWeakHeapObject()) {
     os << "[weak cleared]";
   } else {
@@ -576,6 +577,9 @@ RUNTIME_FUNCTION(Runtime_DebugPrint) {
   }
   os << std::endl;
 
+  // TODO(clemensh): Introduce an output stream which outputs to android log.
+  PrintF("%s", os.str().c_str());
+
   return args[0];  // return TOS
 }