Add a benchmarking_extension API to call TCMalloc's HeapProfilerDump().

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 4acdfed7047091a7850ff849b72465d8f4fa25f9..1eef6493ba51f676a71db3e46f5f2f6e844c2f69 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -319,6 +319,9 @@ const char kEnableGestureTapHighlight[]    = "enable-gesture-tap-highlight";
 // Enables the GPU benchmarking extension
 const char kEnableGpuBenchmarking[]         = "enable-gpu-benchmarking";
 
+// Enables the memory benchmarking extension
+const char kEnableMemoryBenchmarking[]      = "enable-memory-benchmarking";
+
 // Force logging to be enabled.  Logging is disabled by default in release
 // builds.
 const char kEnableLogging[]                 = "enable-logging";