Separate module min memory pages counter for asm.js/WASM.

Currently, V8 uses the same size counter to measure the minimum number of memory pages allocated by a module for both asm.js and WASM. This CL separates the counter into two separate counters, and then uses the appropriate counter when measuring.

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

Review-Url: https://codereview.chromium.org/2781453004
Cr-Commit-Position: refs/heads/master@{#44204}

src/counters.h

@@ -1017,7 +1017,9 @@ class RuntimeCallTimerScope {
   HM(wasm_decode_module_peak_memory_bytes, V8.WasmDecodeModulePeakMemoryBytes) \
   HM(wasm_compile_function_peak_memory_bytes,                                  \
      V8.WasmCompileFunctionPeakMemoryBytes)                                    \
-  HM(wasm_min_mem_pages_count, V8.WasmMinMemPagesCount)                        \
+  /* TODO(karlschimpf) Update chrome flags to reflect asm/wasm split. */       \
+  HM(wasm_asm_min_mem_pages_count, V8.WasmMinMemPagesCount)                    \
+  HM(wasm_wasm_min_mem_pages_count, V8.WasmMinMemPagesCount)                   \
   HM(wasm_max_mem_pages_count, V8.WasmMaxMemPagesCount)                        \
   HM(wasm_function_size_bytes, V8.WasmFunctionSizeBytes)                       \
   HM(wasm_module_size_bytes, V8.WasmModuleSizeBytes)

src/wasm/wasm-module.cc

@@ -1315,7 +1315,9 @@ class InstantiationHelper {
     MaybeHandle<JSArrayBuffer> old_memory;
 
     uint32_t min_mem_pages = module_->min_mem_pages;
-    isolate_->counters()->wasm_min_mem_pages_count()->AddSample(min_mem_pages);
+    (module_->is_wasm() ? isolate_->counters()->wasm_wasm_min_mem_pages_count()
+                        : isolate_->counters()->wasm_asm_min_mem_pages_count())
+        ->AddSample(min_mem_pages);
 
     if (!memory_.is_null()) {
       // Set externally passed ArrayBuffer non neuterable.