[wasm] Add uma stat for asm.js to wasm throuput

BUG=chromium:770618
R=kschimpf@chromium.org,bradnelson@chromium.org,isherman@chromium.org

Change-Id: I33400fb277fff1e92a38753084c518f002685407
Reviewed-on: https://chromium-review.googlesource.com/704228
Commit-Queue: Aseem Garg <aseemgarg@chromium.org>
Reviewed-by: Brad Nelson <bradnelson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48354}

src/asmjs/asm-js.cc

@@ -271,6 +271,17 @@ CompilationJob::Status AsmJsCompilationJob::ExecuteJobImpl() {
                     compilation_info()->literal()->start_position();
   compilation_info()->isolate()->counters()->asm_module_size_bytes()->AddSample(
       module_size);
+  int64_t translate_time_micro = translate_timer.Elapsed().InMicroseconds();
+  int translation_throughput =
+      translate_time_micro != 0
+          ? static_cast<int>(static_cast<int64_t>(module_size) /
+                             translate_time_micro)
+          : 0;
+  compilation_info()
+      ->isolate()
+      ->counters()
+      ->asm_wasm_translation_throughput()
+      ->AddSample(translation_throughput);
   if (FLAG_trace_asm_parser) {
     PrintF(
         "[asm.js translation successful: time=%0.3fms, "

src/counters.h

@@ -1029,7 +1029,9 @@ class RuntimeCallTimerScope {
      V8.AsmWasmTranslationPeakMemoryBytes, 1, GB, 51)                          \
   HR(wasm_compile_function_peak_memory_bytes,                                  \
      V8.WasmCompileFunctionPeakMemoryBytes, 1, GB, 51)                         \
-  HR(asm_module_size_bytes, V8.AsmModuleSizeBytes, 1, GB, 51)
+  HR(asm_module_size_bytes, V8.AsmModuleSizeBytes, 1, GB, 51)                  \
+  HR(asm_wasm_translation_throughput, V8.AsmWasmTranslationThroughput, 1, 100, \
+     20)
 
 #define HISTOGRAM_TIMER_LIST(HT)                                               \
   /* Garbage collection timers. */                                             \