tracing v2: Introduce TraceBufferWriter

components/tracing/core/scattered_stream_writer.cc

 // Copyright 2016 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 "components/tracing/core/scattered_stream_writer.h"
 
 #include <string.h>
 
 #include <algorithm>
 
 #include "base/logging.h"
 
 namespace tracing {
 namespace v2 {
 
+ScatteredStreamWriter::Delegate::~Delegate() {}
+
 ScatteredStreamWriter::ScatteredStreamWriter(Delegate* delegate)
     : delegate_(delegate),
       cur_range_({nullptr, nullptr}),
       write_ptr_(nullptr) {}
 
 ScatteredStreamWriter::~ScatteredStreamWriter() {}
 
 void ScatteredStreamWriter::Reset(ContiguousMemoryRange range) {
   cur_range_ = range;
   write_ptr_ = range.begin;
@@ skipping 29 matching lines @@
     const size_t burst_size = std::min(bytes_available(), bytes_left);
     WriteBytes(src, burst_size);
     bytes_left -= burst_size;
     src += burst_size;
   }
 }
 
 // TODO(primiano): perf optimization: I suspect that at the end this will always
 // be called with |size| == 4, in which case we might just hardcode it.
 ContiguousMemoryRange ScatteredStreamWriter::ReserveBytes(size_t size) {
-  // Assume the reservations are always < TraceRingBuffer::Chunk::kSize.
+  // Assume the reservations are always < kChunkSize.
   if (write_ptr_ + size > cur_range_.end) {
     Extend();
     DCHECK_LE(write_ptr_ + size, cur_range_.end);
   }
   uint8_t* begin = write_ptr_;
   write_ptr_ += size;
 #ifndef NDEBUG
   memset(begin, '\xFF', size);
 #endif
   return {begin, begin + size};
 }
 
 }  // namespace v2
 }  // namespace tracing