Add current_send_quota() accessor to WebSocketChannel

Make the browser's idea of how much quota it has given the renderer
visible outside net::WebSocketChannel. This will be used for
browser-side Blob sending functionality.

See design doc at
https://docs.google.com/document/d/1CDiXB9pBumhFVVfmIn1CRI6v6byxyqWu2urEE9xp714/edit

BUG=571656
TEST=net_unittests

Review URL: https://codereview.chromium.org/1549453003

Cr-Commit-Position: refs/heads/master@{#367777}

2 files changed, 30 insertions, 1 deletions

diff --git a/net/websockets/websocket_channel.h b/net/websockets/websocket_channel.h
index a564270..114bb5e 100644
--- a/net/websockets/websocket_channel.h
+++ b/net/websockets/websocket_channel.h
@@ -98,6 +98,12 @@ class NET_EXPORT WebSocketChannel {
   // processing to OnClosingHandshake() if necessary.
   void StartClosingHandshake(uint16_t code, const std::string& reason);
 
+  // Returns the current send quota. This value is unsafe to use outside of the
+  // browser IO thread because it changes asynchronously.  The value is only
+  // valid for the execution of the current Task or until SendFrame() is called,
+  // whichever happens sooner.
+  int current_send_quota() const { return current_send_quota_; }
+
   // Starts the connection process, using a specified creator callback rather
   // than the default. This is exposed for testing.
   void SendAddChannelRequestForTesting(
diff --git a/net/websockets/websocket_channel_test.cc b/net/websockets/websocket_channel_test.cc
index 5413444..fabd81d 100644
--- a/net/websockets/websocket_channel_test.cc
+++ b/net/websockets/websocket_channel_test.cc
@@ -5,8 +5,8 @@
 #include "net/websockets/websocket_channel.h"
 
 #include <limits.h>
+#include <stddef.h>
 #include <string.h>
-
 #include <iostream>
 #include <iterator>
 #include <string>
@@ -3421,5 +3421,28 @@ TEST_F(WebSocketChannelStreamTimeoutTest, ConnectionCloseTimesOut) {
   completion.WaitForResult();
 }
 
+// Verify that current_send_quota() returns a non-zero value for a newly
+// connected channel.
+TEST_F(WebSocketChannelTest, CurrentSendQuotaNonZero) {
+  CreateChannelAndConnectSuccessfully();
+  EXPECT_GT(channel_->current_send_quota(), 0);
+}
+
+// Verify that current_send_quota() is updated when SendFrame() is called.
+TEST_F(WebSocketChannelTest, CurrentSendQuotaUpdated) {
+  const int kMessageSize = 5;
+  set_stream(make_scoped_ptr(new WriteableFakeWebSocketStream));
+  CreateChannelAndConnectSuccessfully();
+
+  int initial_send_quota = channel_->current_send_quota();
+  EXPECT_GE(initial_send_quota, kMessageSize);
+
+  channel_->SendFrame(
+      true, WebSocketFrameHeader::kOpCodeText,
+      std::vector<char>(static_cast<size_t>(kMessageSize), 'a'));
+  int new_send_quota = channel_->current_send_quota();
+  EXPECT_EQ(kMessageSize, initial_send_quota - new_send_quota);
+}
+
 }  // namespace
 }  // namespace net