Remove collecting data on max memory pages for asm.js, not applicable.

Only WASM has the notion of changing the maximum memory pages. This
CL corrects the UMA stats to only collect this data for WASM only.

BUG=v8:6321
R=bradnelson@chromium.org,bbudge@chromium.org

Review-Url: https://codereview.chromium.org/2845163002
Cr-Commit-Position: refs/heads/master@{#44988}

src/counters.h

@@ -1027,7 +1027,6 @@ class RuntimeCallTimerScope {
      V8.WasmCompileFunctionPeakMemoryBytes)                              \
   HM(wasm_asm_min_mem_pages_count, V8.WasmMinMemPagesCount.asm)          \
   HM(wasm_wasm_min_mem_pages_count, V8.WasmMinMemPagesCount.wasm)        \
-  HM(wasm_asm_max_mem_pages_count, V8.WasmMaxMemPagesCount.asm)          \
   HM(wasm_wasm_max_mem_pages_count, V8.WasmMaxMemPagesCount.wasm)        \
   HM(wasm_asm_function_size_bytes, V8.WasmFunctionSizeBytes.asm)         \
   HM(wasm_wasm_function_size_bytes, V8.WasmFunctionSizeBytes.wasm)       \

src/wasm/wasm-objects.cc

@@ -629,10 +629,9 @@ uint32_t WasmInstanceObject::GetMaxMemoryPages() {
   }
   uint32_t compiled_max_pages = compiled_module()->module()->max_mem_pages;
   Isolate* isolate = GetIsolate();
-  auto* histogram = (compiled_module()->module()->is_wasm()
-                         ? isolate->counters()->wasm_wasm_max_mem_pages_count()
-                         : isolate->counters()->wasm_asm_max_mem_pages_count());
-  histogram->AddSample(compiled_max_pages);
+  assert(compiled_module()->module()->is_wasm());
+  isolate->counters()->wasm_wasm_max_mem_pages_count()->AddSample(
+      compiled_max_pages);
   if (compiled_max_pages != 0) return compiled_max_pages;
   return FLAG_wasm_max_mem_pages;
 }