Implement Math.random() purely in JavaScript.

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 189c215e63904b76aea1dd9493397c2f44f21d2e..3817de104d3b49ce5a4d6adc6d1d0382594fec47 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -185,7 +185,7 @@ enum BindingFlags {
   V(GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX, Map, \
     generator_object_prototype_map) \
   V(GENERATOR_RESULT_MAP_INDEX, Map, generator_result_map) \
-  V(RANDOM_SEED_INDEX, ByteArray, random_seed)
+  V(RANDOM_STATE_INDEX, Smi, random_state)
 
 // JSFunctions are pairs (context, function code), sometimes also called
 // closures. A Context object is used to represent function contexts and
@@ -332,7 +332,7 @@ class Context: public FixedArray {
     STRICT_MODE_GENERATOR_FUNCTION_MAP_INDEX,
     GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX,
     GENERATOR_RESULT_MAP_INDEX,
-    RANDOM_SEED_INDEX,
+    RANDOM_STATE_INDEX,
 
     // Properties from here are treated as weak references by the full GC.
     // Scavenge treats them as strong references.