[wasm] Add timer to measure asm->wasm translation

This will be used for perf tests:
https://chromereviews.googleplex.com/565327014/

R=titzer@chromium.org, bradnelson@chromium.org

Review-Url: https://codereview.chromium.org/2663713003
Cr-Commit-Position: refs/heads/master@{#42807}

src/asmjs/asm-wasm-builder.cc

@@ -1994,6 +1994,9 @@ AsmWasmBuilder::AsmWasmBuilder(CompilationInfo* info)
 // TODO(aseemgarg): probably should take zone (to write wasm to) as input so
 // that zone in constructor may be thrown away once wasm module is written.
 AsmWasmBuilder::Result AsmWasmBuilder::Run(Handle<FixedArray>* foreign_args) {
+  HistogramTimerScope asm_wasm_time_scope(
+      info_->isolate()->counters()->asm_wasm_translation_time());
+
   Zone* zone = info_->zone();
   AsmWasmBuilderImpl impl(info_->isolate(), zone, info_,
                           info_->parse_info()->ast_value_factory(),

src/counters.h

@@ -983,6 +983,8 @@ class RuntimeCallTimerScope {
   HT(wasm_compile_module_time, V8.WasmCompileModuleMicroSeconds, 1000000,      \
      MICROSECOND)                                                              \
   HT(wasm_compile_function_time, V8.WasmCompileFunctionMicroSeconds, 1000000,  \
+     MICROSECOND)                                                              \
+  HT(asm_wasm_translation_time, V8.AsmWasmTranslationMicroSeconds, 1000000,    \
      MICROSECOND)
 
 #define AGGREGATABLE_HISTOGRAM_TIMER_LIST(AHT) \