Use filter context to track stats better in SDCH filtering

net/url_request/url_request_job.cc

Index: net/url_request/url_request_job.cc
===================================================================
--- net/url_request/url_request_job.cc	(revision 11636)
+++ net/url_request/url_request_job.cc	(working copy)
@@ -28,7 +28,8 @@
       read_buffer_(NULL),
       read_buffer_len_(0),
       has_handled_response_(false),
-      expected_content_size_(-1) {
+      expected_content_size_(-1),
+      filter_input_byte_count_(0) {
   is_profiling_ = request->enable_profiling();
   if (is_profiling()) {
     metrics_.reset(new URLRequestJobMetrics());
@@ -86,6 +87,10 @@
   NOTREACHED();
 }
 
+int64 URLRequestJob::GetByteReadCount() const {
+  return filter_input_byte_count_ ;
+}
+
 bool URLRequestJob::GetURL(GURL* gurl) const {
   if (!request_)
     return false;
@@ -505,6 +510,7 @@
     ++(metrics_->number_of_read_IO_);
     metrics_->total_bytes_read_ += bytes_read;
   }
+  filter_input_byte_count_ += bytes_read;
   g_url_request_job_tracker.OnBytesRead(this, bytes_read);
 }