Revert of Debugger: use a Map to cache mirrors.

src/debug/mirrors.js

Index: src/debug/mirrors.js
diff --git a/src/debug/mirrors.js b/src/debug/mirrors.js
index 31387abc95c8bc319f3a36f38444b8ea55eb310a..85ff2b2a90e3cae5eb10ee852cd8ef6f870f451f 100644
--- a/src/debug/mirrors.js
+++ b/src/debug/mirrors.js
@@ -11,7 +11,6 @@
 var GlobalArray = global.Array;
 var IsNaN = global.isNaN;
 var JSONStringify = global.JSON.stringify;
-var GlobalMap = global.Map;
 var MathMin = global.Math.min;
 
 // ----------------------------------------------------------------------------
@@ -74,12 +73,12 @@
 var next_transient_handle_ = -1;
 
 // Mirror cache.
-var mirror_cache_ = new GlobalMap();
+var mirror_cache_ = [];
 var mirror_cache_enabled_ = true;
 
 
 function MirrorCacheIsEmpty() {
-  return mirror_cache_.size === 0;
+  return next_handle_ == 0 && mirror_cache_.length == 0;
 }
 
 
@@ -91,7 +90,7 @@
 
 function ClearMirrorCache(value) {
   next_handle_ = 0;
-  mirror_cache_.clear();
+  mirror_cache_ = [];
 }
 
 
@@ -121,7 +120,17 @@
 
   // Look for non transient mirrors in the mirror cache.
   if (!opt_transient && mirror_cache_enabled_) {
-    if (mirror_cache_.has(value)) return mirror_cache_.get(value);
+    for (var id in mirror_cache_) {
+      mirror = mirror_cache_[id];
+      if (mirror.value() === value) {
+        return mirror;
+      }
+      // Special check for NaN as NaN == NaN is false.
+      if (mirror.isNumber() && IsNaN(mirror.value()) &&
+          typeof value == 'number' && IsNaN(value)) {
+        return mirror;
+      }
+    }
   }
 
   if (IS_UNDEFINED(value)) {
@@ -162,7 +171,7 @@
     mirror = new ObjectMirror(value, MirrorType.OBJECT_TYPE, opt_transient);
   }
 
-  if (mirror_cache_enabled_) mirror_cache_.set(value, mirror);
+  if (mirror_cache_enabled_) mirror_cache_[mirror.handle()] = mirror;
   return mirror;
 }
 
@@ -178,10 +187,7 @@
   if (!mirror_cache_enabled_) {
     throw MakeError(kDebugger, "Mirror cache is disabled");
   }
-  for (var value of mirror_cache_.values()) {
-    if (value.handle() == handle) return value;
-  }
-  return UNDEFINED;
+  return mirror_cache_[handle];
 }