Mark precompilation_dart2js_test as slow in debug mode.

tests/standalone/standalone.status

Index: tests/standalone/standalone.status
diff --git a/tests/standalone/standalone.status b/tests/standalone/standalone.status
index 397ea2f0b74b73f244ee34f02a9681a2a64c1349..009a4acba3861b8b32e604bff5454452a804f37b 100644
--- a/tests/standalone/standalone.status
+++ b/tests/standalone/standalone.status
@@ -110,16 +110,19 @@ precompilation_test: Skip # Standalone only test.
 precompilation_dart2js_test: Skip # Standalone only test.
 noopt_test: Skip # Standalone only test.
 
-[ $runtime == vm && $arch == ia32]
+[ $runtime == vm && $mode == debug ]
+precompilation_dart2js_test: Slow
+
+[ $runtime == vm && $arch == ia32 ]
 precompilation_test: Skip # Not expected to pass on ia32.
 precompilation_dart2js_test: Skip # Not expected to pass on ia32.
 noopt_test: Skip # Not expected to pass on ia32.
 
-[ $runtime == vm && $arch == arm]
+[ $runtime == vm && $arch == arm ]
 precompilation_test: Skip # Issue 24427
 precompilation_dart2js_test: Skip # Issue 24427
 
-[ $runtime == vm && $arch == mips]
+[ $runtime == vm && $arch == mips ]
 precompilation_dart2js_test: SkipSlow
 
 [ $compiler == dart2js && $jscl ]