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

base/profiler/native_stack_sampler.cc

Index: base/profiler/native_stack_sampler.cc
diff --git a/base/profiler/native_stack_sampler.cc b/base/profiler/native_stack_sampler.cc
index 968455f13e007c7b2c26290249a79883c8805d2d..32c4a7552e74861f43314ac3671e1c3e009aeb27 100644
--- a/base/profiler/native_stack_sampler.cc
+++ b/base/profiler/native_stack_sampler.cc
@@ -6,6 +6,11 @@
 
 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() {}