Add a histogram for renderer memory usage.

webkit/glue/webkit_glue.h

Index: webkit/glue/webkit_glue.h
diff --git a/webkit/glue/webkit_glue.h b/webkit/glue/webkit_glue.h
index d5c1991380b8c330ff5a1232c43f6c307ed988c2..d9c48b4d27ed8f49fa5c03199ea52801b6dfa902 100644
--- a/webkit/glue/webkit_glue.h
+++ b/webkit/glue/webkit_glue.h
@@ -114,6 +114,12 @@ WEBKIT_GLUE_EXPORT bool IsInspectorProtocolVersionSupported(
 WEBKIT_GLUE_EXPORT void ConfigureURLRequestForReferrerPolicy(
     net::URLRequest* request, WebKit::WebReferrerPolicy referrer_policy);
 
+// Returns an estimate of the memory usage of the renderer process. Different
+// platforms implement this function differently, and count in different
+// allocations. Results are not comparable across platforms. The estimate is
+// computed inside the sandbox and thus its not always accurate.
+WEBKIT_GLUE_EXPORT size_t MemoryUsageKB();
+
 }  // namespace webkit_glue
 
 #endif  // WEBKIT_GLUE_WEBKIT_GLUE_H_