Make sure that ScratchBuffer::Allocate() always return 8-byte aligned address.

mojo/public/cpp/bindings/lib/scratch_buffer.cc

 // Copyright 2014 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/cpp/bindings/lib/scratch_buffer.h"
 
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ skipping 62 matching lines @@
 }
 
 bool ScratchBuffer::AddOverflowSegment(size_t delta) {
   if (delta < kMinSegmentSize)
     delta = kMinSegmentSize;
 
   if (delta > kMaxSegmentSize)
     return false;
 
   // Ensure segment buffer is aligned.
-  size_t segment_size = internal::Align(sizeof(Segment)) + delta;
-  Segment* segment = static_cast<Segment*>(malloc(segment_size));
+  size_t padded_segment_size = internal::Align(sizeof(Segment));
+  Segment* segment = static_cast<Segment*>(
+      malloc(padded_segment_size + delta));
   if (segment) {
     segment->next = overflow_;
-    segment->cursor = reinterpret_cast<char*>(segment + 1);
+    segment->cursor = reinterpret_cast<char*>(segment) + padded_segment_size;

[darin (slow to review), 2014/05/05 22:55:52]

good catch!

     segment->end = segment->cursor + delta;
     overflow_ = segment;
     return true;
   }
 
   return false;
 }
 
 }  // namespace internal
 }  // namespace mojo