[wasm][asm.js] Make asm.js -> wasm message allocations predictable.

We allocate console timing messages for now,
as previously skipping this tickled unrelated flake.
Use a fixed message to make them consistent in predictable mode.

BUG=v8:4203
TBR=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2628173003
Cr-Commit-Position: refs/heads/master@{#42303}

src/asmjs/asm-js.cc

@@ -212,9 +212,15 @@ MaybeHandle<FixedArray> AsmJs::CompileAsmViaWasm(CompilationInfo* info) {
   MessageLocation location(info->script(), info->literal()->position(),
                            info->literal()->position());
   char text[100];
-  int length = base::OS::SNPrintF(
-      text, arraysize(text), "success, asm->wasm: %0.3f ms, compile: %0.3f ms",
-      asm_wasm_time, compile_time);
+  int length;
+  if (FLAG_predictable) {
+    length = base::OS::SNPrintF(text, arraysize(text), "success");
+  } else {
+    length =
+        base::OS::SNPrintF(text, arraysize(text),
+                           "success, asm->wasm: %0.3f ms, compile: %0.3f ms",
+                           asm_wasm_time, compile_time);
+  }
   DCHECK_NE(-1, length);
   USE(length);
   Handle<String> stext(info->isolate()->factory()->InternalizeUtf8String(text));
@@ -321,9 +327,13 @@ MaybeHandle<Object> AsmJs::InstantiateAsmWasm(i::Isolate* isolate,
   }
   MessageLocation location(script, position, position);
   char text[50];
-  int length =
-      base::OS::SNPrintF(text, arraysize(text), "success, %0.3f ms",
-                         instantiate_timer.Elapsed().InMillisecondsF());
+  int length;
+  if (FLAG_predictable) {
+    length = base::OS::SNPrintF(text, arraysize(text), "success");
+  } else {
+    length = base::OS::SNPrintF(text, arraysize(text), "success, %0.3f ms",
+                                instantiate_timer.Elapsed().InMillisecondsF());
+  }
   DCHECK_NE(-1, length);
   USE(length);
   Handle<String> stext(isolate->factory()->InternalizeUtf8String(text));