Remove obsolete try/catch from ObjectIsPromise().

src/debug/mirrors.js

Index: src/debug/mirrors.js
diff --git a/src/debug/mirrors.js b/src/debug/mirrors.js
index e77f7a0f2ba7053944c7a13649ee41ac4bdf8c27..11f9e485c13be252986a228826de69c9ea83bf5c 100644
--- a/src/debug/mirrors.js
+++ b/src/debug/mirrors.js
@@ -107,16 +107,9 @@ function ClearMirrorCache(value) {
 }
 
 
-// Wrapper to check whether an object is a Promise.  The call may not work
-// if promises are not enabled.
-// TODO(yangguo): remove try-catch once promises are enabled by default.
 function ObjectIsPromise(value) {
-  try {
-    return IS_SPEC_OBJECT(value) &&
-           !IS_UNDEFINED(%DebugGetProperty(value, promiseStatusSymbol));
-  } catch (e) {
-    return false;
-  }
+  return IS_SPEC_OBJECT(value) &&
+         !IS_UNDEFINED(%DebugGetProperty(value, promiseStatusSymbol));
 }