[wasm] Introduce custom asm.js bytecodes for double->int conversions.

src/wasm/asm-wasm-builder.cc

Index: src/wasm/asm-wasm-builder.cc
diff --git a/src/wasm/asm-wasm-builder.cc b/src/wasm/asm-wasm-builder.cc
index 3a0b5692ad4c7ad3e947ade9ca321424850638ae..d517a166ba5f64735259302ebe46e339b64368cf 100644
--- a/src/wasm/asm-wasm-builder.cc
+++ b/src/wasm/asm-wasm-builder.cc
@@ -1437,9 +1437,9 @@ class AsmWasmBuilderImpl : public AstVisitor {
       RECURSE(Visit(GetLeft(expr)));
       TypeIndex type = TypeIndexOf(GetLeft(expr));
       if (type == kFloat32) {
-        current_function_builder_->Emit(kExprI32SConvertF32);
+        current_function_builder_->Emit(kExprI32AsmjsSConvertF32);
       } else if (type == kFloat64) {
-        current_function_builder_->Emit(kExprI32SConvertF64);
+        current_function_builder_->Emit(kExprI32AsmjsSConvertF64);
       } else {
         UNREACHABLE();
       }