A change for the setPause() api in chrome.sockets.tcp:

extensions/browser/api/socket/tcp_socket.h

Index: extensions/browser/api/socket/tcp_socket.h
diff --git a/extensions/browser/api/socket/tcp_socket.h b/extensions/browser/api/socket/tcp_socket.h
index 40dd5fd7fd9163ce1e1de75937c689e7b2e61445..4216d467c0dc9e7943cc7a7d04449555ee4ba96a 100644
--- a/extensions/browser/api/socket/tcp_socket.h
+++ b/extensions/browser/api/socket/tcp_socket.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "extensions/browser/api/socket/passthrough.h"
 #include "extensions/browser/api/socket/socket.h"
 
 // This looks like it should be forward-declarable, but it does some tricky
@@ -19,6 +20,180 @@ class Socket;
 }
 
 namespace extensions {
+typedef base::Callback<void(void)> PauseCompletionCallback;

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

nit: please use a type alias instead of typedef now

+
+// A wrapper around an existing TCPClientSocket with an internal read buffer
+// to support immediate pausing.  If this socket is paused while it still has
+// a pending Read() on its wrapped socket, this socket will buffer the data
+// returned.  Further invocations of BufferingStreamSocket::Read() will
+// first return all data from the internal buffer, before causing Read()s on
+// the underlying TCP socket. Other than the buffering Read() behavior,
+// BufferingStreamSocket acts identically to the net::TCPClientSocket that
+// it wraps.
+class SocketPauseBuffer {

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

This class should be in its own header and cc file

+ public:
+  typedef base::Callback<

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

nit: type alias

+      int(net::IOBuffer*, int, const net::CompletionCallback&)>
+      DownstreamReadCallback;
+
+  // Pass in the Read() method of the underlying socket that needs pausing
+  // added to it.
+  explicit SocketPauseBuffer(
+      const DownstreamReadCallback& downstream_read_callback);
+  ~SocketPauseBuffer();
+
+  // Return from any pending Read() immediately, invoking the callback.
+  // BufferingStreamSocket will then buffer data received from any pending
+  // Read() that it may have invoked on the underlying socket. Subsequent
+  // Read() calls will have their callbacks posted immediately with data from
+  // the buffer until it is drained. When there is no buffered data, Read()
+  // acts exactly as net::TCPClientSocket::Read() until there is another
+  // invocation to Pause().  Returns true unless DisableBuffering() has been
+  // called.
+  bool Pause();
+
+  // Turn into a pure pass-through object, with no internal buffer and no
+  // ability to Pause() successfully.  Any pending Read() invocation is
+  // unaffected, preserving its internal buffer until that Read() completes.
+  void DisableBuffering();
+
+  // This Read() can return early when pausing via Pause(). It will return
+  // (via callback) ERR_ABORTED. Without interference from Pause(), Read()
+  // acts identically to net::TCPClientSocket::Read().
+  int Read(net::IOBuffer* buffer,
+           int buf_len,
+           const net::CompletionCallback& callback);
+
+ private:
+  // Callback passed to downstream socket's Read().
+  void ReadComplete(int count);
+
+  // Buffer state printer.
+  std::string StatusDescription();
+
+  // 'Buffered' in the diagram below.
+  int BufferedDataCount() const;
+
+  // Records that |num_incoming_bytes| has been added to the buffered amount.
+  void CreditIncomingData(int num_incoming_bytes);
+
+  // Copies data from downstream_read_buffer_ to |dest|, and marks that data
+  // as having been returned upstream.
+  void ReturnDataInBuffer(net::IOBuffer* dest, int num_outgoing_bytes);
+
+  // Shift the buffered data left, freeing buffer space of data that's
+  // already been given back upstream.
+  void FreeReturnedBufferSpace();
+
+  // Expands buffer if there isn't |num_bytes| of open space left.
+  void InsureBufferCanHold(int num_bytes);

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

nit: s/Insure/Ensure/

+
+  // Flush upstream state, usually after having returned a value without
+  // invoking the callback.
+  void ResetUpstreamState();
+
+  // Will also reset upstream state, and re-entrantly invoke the callback.
+  void InvokeCallback(int result);
+
+  // Whether a downstream read has been issued with an expected invocation of
+  // ReadComplete().
+  bool read_issued_;
+
+  // Terminology: clients of BufferingStreamSocket are 'upstream', and
+  // BufferingStreamSocket is a client of downstream_socket_.

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

downstream_socket_ doesn't exist

+  DownstreamReadCallback downstream_read_cb_;
+  //  scoped_ptr<net::StreamSocket> downstream_socket_;

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

Remove this?

+
+  // A GrowableIOBuffer that BufferingStreamSocket::Read passes
+  // downstream.  The offset state is used to store where in the buffer has
+  // already been stored, and where data from the next pending read will go.
+  //
+  // The buffer's state has this structure:
+  // 0                             offset()
+  // +------------------+----------+--------------------------------------+
+  // | already returned | buffered | open space for other downstream reads|
+  // +------------------+----------+--------------------------------------+
+  //                    ^ upstream_data_returned_
+  //
+  // These are represented as integers, counting bytes of buffer.  The amount
+  // already returned is kept in upstream_data_returned_.  The end of the
+  // buffered region is stored in downstream_read_buffer_->offset().  The
+  // remaining open space is the remaining |capacity| of
+  // downstream_read_buffer_.  The buffer is compacted (e.g., already
+  // returned data flushed) before every downstream Read().
+  scoped_refptr<net::GrowableIOBuffer> downstream_read_buffer_;
+
+  // The amount of data in downstream_read_buffer_ that's already been
+  // returned upstream.
+  int upstream_data_returned_;
+  int upstream_read_buffer_offset_;
+  // A saved error code when a downstream read returns one, and there is no
+  // callback to pass it back to.
+  int prior_error_code_;
+
+  // The callback, IOBuffer, and requested read amount passed into
+  // BufferingStreamSocket::Read.
+  net::CompletionCallback upstream_read_callback_;
+  scoped_refptr<net::IOBuffer> upstream_read_buffer_;
+  int upstream_read_request_size_;
+  bool buffering_disabled_;
+};
+
+// Passthrough to a StreamSocket, but integrates a SocketPauseBuffer for
+// reading.
+class BufferingStreamSocket : public Passthrough<net::StreamSocket> {

[Ken Rockot(use gerrit already), 2015/12/15 17:17:48]

This class should have its own header and cc

+ public:
+  explicit BufferingStreamSocket(scoped_ptr<net::StreamSocket> socket);
+  ~BufferingStreamSocket() override;
+
+  bool Pause();
+  void DisableBuffering();
+
+  // This Read() can return early when pausing via Pause(). It will return
+  // (via callback) ERR_ABORTED. Without interference from Pause(), Read()
+  // acts identically to net::TCPClientSocket::Read().
+  int Read(net::IOBuffer* buffer,
+           int buf_len,
+           const net::CompletionCallback& callback) override;
+
+ private:
+  SocketPauseBuffer pause_buffer_;
+};
+
+template <>
+class DefaultInitializer<net::TCPClientSocket> : public net::TCPClientSocket {
+ public:
+  DefaultInitializer()
+      : net::TCPClientSocket(net::AddressList(),
+                             nullptr,
+                             net::NetLog::Source()) {}
+};
+
+// Passthrough to a TCPClientSocket, but integrates a SocketPauseBuffer for
+// reading.
+class BufferingTCPClientSocket : public Passthrough<net::TCPClientSocket> {

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

This class should have its own header and cc

+ public:
+  explicit BufferingTCPClientSocket(scoped_ptr<net::TCPClientSocket> socket);
+  ~BufferingTCPClientSocket() override;
+
+  bool Pause();
+  void DisableBuffering();
+
+  // This Read() can return early when pausing via Pause(). It will return
+  // (via callback) ERR_ABORTED. Without interference from Pause(), Read()
+  // acts identically to net::TCPClientSocket::Read().
+  int Read(net::IOBuffer* buffer,
+           int buf_len,
+           const net::CompletionCallback& callback) override;
+
+  // Additional pass-through APIs for TCPClientSocket (vs Passthrough<>'s
+  // implementation of just StreamSocket.
+  bool SetKeepAlive(bool enable, int delay) override;
+  bool SetNoDelay(bool no_delay) override;
+
+ private:
+  SocketPauseBuffer pause_buffer_;
+};
 
 class TCPSocket : public Socket {
  public:
@@ -69,7 +244,7 @@ class TCPSocket : public Socket {
 
   // Returns NULL if GetSocketType() isn't TYPE_TCP or if the connection
   // wasn't set up via Connect() (vs Listen()/Accept()).
-  net::TCPClientSocket* ClientStream();
+  virtual BufferingTCPClientSocket* ClientStream();
 
   // Whether a Read() has been issued, that hasn't come back yet.
   bool HasPendingRead() const;
@@ -88,7 +263,7 @@ class TCPSocket : public Socket {
   TCPSocket(net::TCPServerSocket* tcp_server_socket,
             const std::string& owner_extension_id);
 
-  scoped_ptr<net::TCPClientSocket> socket_;
+  scoped_ptr<BufferingTCPClientSocket> socket_;
   scoped_ptr<net::TCPServerSocket> server_socket_;
 
   enum SocketMode { UNKNOWN = 0, CLIENT, SERVER, };
@@ -112,6 +287,8 @@ class ResumableTCPSocket : public TCPSocket {
                               const std::string& owner_extension_id,
                               bool is_connected);
 
+  ~ResumableTCPSocket() override;
+
   // Overriden from ApiResource
   bool IsPersistent() const override;
 
@@ -127,6 +304,15 @@ class ResumableTCPSocket : public TCPSocket {
   bool paused() const { return paused_; }
   void set_paused(bool paused) { paused_ = paused; }
 
+  void set_api_pause_complete_callback(
+      const PauseCompletionCallback& callback) {
+    pause_callback_ = callback;
+  }
+
+  // Tell this socket that it's pause has actually finished, and it can
+  // invoke pause callback.
+  void ApiPauseComplete();

[Ken Rockot(use gerrit already), 2015/12/15 17:17:49]

nit: How about NotifyPauseComplete?

+
  private:
   friend class ApiResourceManager<ResumableTCPSocket>;
   static const char* service_name() { return "ResumableTCPSocketManager"; }
@@ -141,6 +327,8 @@ class ResumableTCPSocket : public TCPSocket {
   // Flag indicating whether a connected socket blocks its peer from sending
   // more data - see sockets_tcp.idl.
   bool paused_;
+  // An optional callback to save and invoke from ResumableTCPServerSocket.
+  PauseCompletionCallback pause_callback_;
 };
 
 // TCP Socket instances from the "sockets.tcpServer" namespace. These are