asm.js. Adds support for clz32 in asm.js.

src/asmjs/asm-wasm-builder.cc

Index: src/asmjs/asm-wasm-builder.cc
diff --git a/src/asmjs/asm-wasm-builder.cc b/src/asmjs/asm-wasm-builder.cc
index 9ac748bdd0f4b553327ecbe0c32855372b45cc68..644edc47b6e671f480301ebdb80d5306d5e85a6b 100644
--- a/src/asmjs/asm-wasm-builder.cc
+++ b/src/asmjs/asm-wasm-builder.cc
@@ -1085,6 +1085,12 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
         }
         break;
       }
+      case AsmTyper::kMathClz32: {
+        VisitCallArgs(call);
+        DCHECK(call_type == kAstI32);
+        current_function_builder_->Emit(kExprI32Clz);
+        break;
+      }
       case AsmTyper::kMathAbs: {
         if (call_type == kAstI32) {
           uint32_t tmp = current_function_builder_->AddLocal(kAstI32);