Have ScratchBuffer::Allocate prefer allocating on the stack even if a previous

mojo/public/bindings/lib/buffer.cc

Index: mojo/public/bindings/lib/buffer.cc
diff --git a/mojo/public/bindings/lib/buffer.cc b/mojo/public/bindings/lib/buffer.cc
index b5b9e7d815a4d6533686b3e9b6aca13f866c34ab..3ad964629ca1d2f1d47f3fc130e6097dc41e4fc2 100644
--- a/mojo/public/bindings/lib/buffer.cc
+++ b/mojo/public/bindings/lib/buffer.cc
@@ -34,13 +34,18 @@ ScratchBuffer::~ScratchBuffer() {
 void* ScratchBuffer::Allocate(size_t delta) {
   delta = internal::Align(delta);
 
-  void* result =
-      AllocateInSegment((overflow_ != NULL) ? overflow_ : &fixed_, delta);
+  void* result = AllocateInSegment(&fixed_, delta);
   if (result)
     return result;
 
+  if (overflow_) {
+    result = AllocateInSegment(overflow_, delta);
+    if (result)
+      return result;
+  }
+
   AddOverflowSegment(delta);
-  return Allocate(delta);
+  return AllocateInSegment(overflow_, delta);
 }
 
 void* ScratchBuffer::AllocateInSegment(Segment* segment, size_t delta) {