Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/http2_priority_dependencies.h

Index: net/spdy/http2_priority_dependencies.h
diff --git a/net/spdy/http2_priority_dependencies.h b/net/spdy/http2_priority_dependencies.h
index d356a79586a63a3307f27c59555b9ddc6908c3c1..5a5aed3554ca220ce0096b5567d4f6343bb9454c 100644
--- a/net/spdy/http2_priority_dependencies.h
+++ b/net/spdy/http2_priority_dependencies.h
@@ -47,6 +47,9 @@ class NET_EXPORT_PRIVATE Http2PriorityDependencies {
   std::vector<DependencyUpdate> OnStreamUpdate(SpdyStreamId id,
                                                SpdyPriority new_priority);
 
+  // Returns the estimate of dynamically allocated memory in bytes.
+  size_t EstimateMemoryUsage() const;
+
  private:
   // The requirements for the internal data structure for this class are:
   //     a) Constant time insertion of entries at the end of the list,