[wasm] Adding metrics for Asm/Wasm.

src/wasm/wasm-js.cc

Index: src/wasm/wasm-js.cc
diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index 83009d7c81def5acbd56bc711fc5f2c5528db216..eb21796fca46cb079bab351a3d45ba47713d4365 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -195,6 +195,8 @@ void InstantiateModuleCommon(const v8::FunctionCallbackInfo<v8::Value>& args,
   }
 
   if (result.val) delete result.val;
+  isolate->counters()->wasm_instantiate_peak_memory()->AddSample(
+      static_cast<int>(zone.allocation_size()));

[ahaas, 2016/04/11 08:03:08]

What exactly do you want to measure with this counter? When I first looked at
this code I thought this counter measures the peak memory consumption for the
whole module instantiation. However, the zone you measure is only used to decode
a wasm module, and there are also other zones in use to instantiate a module.
For example, there exists a zone to construct the graph in
wasm-compiler.cc::CompileWasmFunction, and there exists a whole zone pool in
pipeline.cc::GenerateCodeForTesting to compile the graph.

[bradn, 2016/04/13 00:22:45]

Erg, yeah this one doesn't make much sense.
Ideally I might aggregate them, but more important to get some measurements in
before the branch.
Dropping this one.

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