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

mojo/public/tests/buffer_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/public/bindings/lib/bindings_serialization.h"
 #include "mojo/public/bindings/lib/buffer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 namespace test {
@@ skipping 14 matching lines @@
   void* small = buf.Allocate(10);
   EXPECT_TRUE(small >= &buf && small < (&buf + sizeof(buf)));
   EXPECT_TRUE(IsZero(small, 10));
 
   // Large allocations won't be on the stack.
   void* large = buf.Allocate(100*1024);
   EXPECT_TRUE(IsZero(large, 100*1024));
   EXPECT_FALSE(large >= &buf && large < (&buf + sizeof(buf)));
 
   // But another small allocation should be back on the stack.
-  // TODO(mpcomplete): but it isn't. We can fix that easily enough.
   small = buf.Allocate(10);
   EXPECT_TRUE(IsZero(small, 10));
-  //EXPECT_TRUE(small >= &buf && small < (&buf + sizeof(buf)));
+  EXPECT_TRUE(small >= &buf && small < (&buf + sizeof(buf)));
 }
 
 // Tests that FixedBuffer allocates memory aligned to 8 byte boundaries.
 TEST(FixedBufferTest, Alignment) {
   FixedBuffer buf(internal::Align(10) * 2);
   ASSERT_EQ(buf.size(), 16u * 2);
 
   void* a = buf.Allocate(10);
   ASSERT_TRUE(a);
   EXPECT_TRUE(IsZero(a, 10));
@@ skipping 29 matching lines @@
   }
 
   // Since we called Leak, ptr is still writable after FixedBuffer went out of
   // scope.
   memset(ptr, 1, 8);
   free(buf_ptr);
 }
 
 }  // namespace test
 }  // namespace mojo