Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/spdy_header_block.cc

Index: net/spdy/spdy_header_block.cc
diff --git a/net/spdy/spdy_header_block.cc b/net/spdy/spdy_header_block.cc
index 6cbd6ba645c4585a3126099322effb3f9525c968..eb798a0f3fddb274df11bca9b91e3e1b4312d535 100644
--- a/net/spdy/spdy_header_block.cc
+++ b/net/spdy/spdy_header_block.cc
@@ -11,6 +11,7 @@
 
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/trace_event/memory_usage_estimator.h"
 #include "base/values.h"
 #include "net/base/arena.h"
 #include "net/http/http_log_util.h"
@@ -89,6 +90,11 @@ class SpdyHeaderBlock::Storage {
 
   size_t bytes_allocated() const { return arena_.status().bytes_allocated(); }
 
+  // TODO(xunjieli): https://crbug.com/669108. Merge this with bytes_allocated()
+  size_t EstimateMemoryUsage() const {
+    return arena_.status().bytes_allocated();
+  }
+
  private:
   UnsafeArena arena_;
 };
@@ -299,6 +305,12 @@ void SpdyHeaderBlock::AppendValueOrAddHeader(const StringPiece key,
   iter->second.Append(GetStorage()->Write(value));
 }
 
+size_t SpdyHeaderBlock::EstimateMemoryUsage() const {
+  // TODO(xunjieli): https://crbug.com/669108. Also include |block_| when EMU()
+  // supports linked_hash_map.
+  return base::trace_event::EstimateMemoryUsage(storage_);
+}
+
 void SpdyHeaderBlock::AppendHeader(const StringPiece key,
                                    const StringPiece value) {
   auto storage = GetStorage();