Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/header_coalescer.h

Index: net/spdy/header_coalescer.h
diff --git a/net/spdy/header_coalescer.h b/net/spdy/header_coalescer.h
index fe30a2896a98b960f8c36ff3e15c6c708aa1b51d..f6151390d6fb2cf9f2574c4bb07e5d7c69caf9ef 100644
--- a/net/spdy/header_coalescer.h
+++ b/net/spdy/header_coalescer.h
@@ -26,6 +26,9 @@ class NET_EXPORT_PRIVATE HeaderCoalescer : public SpdyHeadersHandlerInterface {
   SpdyHeaderBlock release_headers();
   bool error_seen() const { return error_seen_; }
 
+  // Returns the estimate of dynamically allocated memory in bytes.
+  size_t EstimateMemoryUsage() const;
+
  private:
   SpdyHeaderBlock headers_;
   bool headers_valid_ = true;