Separate decoding module peak memory bytes for asm/wasm.

Currently, V8 uses the same counter to measue module decoding peak memory bytes
for both asm.js and WASM. This CL separates the counter into two separate
counters, and then uses the appropriate counter when decoding a module.

BUG=chromium:704922
R=bbudge@chromium.org,bradnelson@chromium.org,mtrofin@chromium.org

Review-Url: https://codereview.chromium.org/2778973003
Cr-Commit-Position: refs/heads/master@{#44207}

src/counters.h

@@ -1014,7 +1014,11 @@ class RuntimeCallTimerScope {
   HM(memory_heap_committed, V8.MemoryHeapCommitted)                      \
   HM(memory_heap_used, V8.MemoryHeapUsed)                                \
   /* Asm/Wasm */                                                         \
-  HM(wasm_decode_module_peak_memory_bytes, V8.WasmDecodeModulePeakMemoryBytes) \
+  /* TODO(karlschimpf) Update chrome flags to reflect asm/wasm split. */ \
+  HM(wasm_decode_asm_module_peak_memory_bytes,                           \
+     V8.WasmDecodeModulePeakMemoryBytes)                                 \
+  HM(wasm_decode_wasm_module_peak_memory_bytes,                          \
+     V8.WasmDecodeModulePeakMemoryBytes)                                 \
   HM(wasm_compile_function_peak_memory_bytes,                            \
      V8.WasmCompileFunctionPeakMemoryBytes)                              \
   /* TODO(karlschimpf) Update chrome flags to reflect asm/wasm split. */ \

src/wasm/module-decoder.cc

@@ -1173,8 +1173,10 @@ ModuleResult DecodeWasmModule(Isolate* isolate, const byte* module_start,
   // TODO(titzer): this isn't accurate, since it doesn't count the data
   // allocated on the C++ heap.
   // https://bugs.chromium.org/p/chromium/issues/detail?id=657320
-  isolate->counters()->wasm_decode_module_peak_memory_bytes()->AddSample(
-      static_cast<int>(zone->allocation_size()));
+  (IsWasm(origin)
+       ? isolate->counters()->wasm_decode_wasm_module_peak_memory_bytes()
+       : isolate->counters()->wasm_decode_asm_module_peak_memory_bytes())
+      ->AddSample(static_cast<int>(zone->allocation_size()));
   return result;
 }