Use a common buffer across all instances for stack-copy.

base/profiler/native_stack_sampler.cc

 // Copyright 2015 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 "base/profiler/native_stack_sampler.h"
 
 namespace base {
 
+NativeStackSampler::StackBuffer::StackBuffer(size_t buffer_size)
+    : buffer_(new unsigned char[buffer_size]), size_(buffer_size) {}

[Mike Wittman, 2017/05/10 01:29:56]

We should fix this for alignment while we're here, since the pointer returned by
"new unsigned char[buffer_size]" is only guaranteed to be one byte aligned. The
value returned by buffer() should be word aligned to avoid the performance
penalty of unaligned reads/writes on x64.

[bcwhite, 2017/05/10 13:50:37]

Done.

+
+NativeStackSampler::StackBuffer::~StackBuffer() {}
+
 NativeStackSampler::NativeStackSampler() {}
 
 NativeStackSampler::~NativeStackSampler() {}
 
 NativeStackSamplerTestDelegate::~NativeStackSamplerTestDelegate() {}
 
 NativeStackSamplerTestDelegate::NativeStackSamplerTestDelegate() {}
 
 }  // namespace base