Add duplicate parameter detection to preparser.

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 331c01add80495ea94b7a7331a2687bb07771796..f62696a1d372cf751c6d52286c39441f0c6b8a74 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -496,9 +496,6 @@ class Collector {
  public:
   explicit Collector(int initial_capacity = kMinCapacity)
       : index_(0), size_(0) {
-    if (initial_capacity < kMinCapacity) {
-      initial_capacity = kMinCapacity;
-    }
     current_chunk_ = Vector<T>::New(initial_capacity);
   }
 
@@ -600,13 +597,21 @@ class Collector {
   // Creates a new current chunk, and stores the old chunk in the chunks_ list.
   void Grow(int min_capacity) {
     ASSERT(growth_factor > 1);
-    int growth = current_chunk_.length() * (growth_factor - 1);
-    if (growth > max_growth) {
-      growth = max_growth;
-    }
-    int new_capacity = current_chunk_.length() + growth;
-    if (new_capacity < min_capacity) {
-      new_capacity = min_capacity + growth;
+    int new_capacity;
+    int current_length = current_chunk_.length();
+    if (current_length < kMinCapacity) {
+      // The collector started out as empty.
+      new_capacity = min_capacity * growth_factor;
+      if (new_capacity < kMinCapacity) new_capacity = kMinCapacity;
+    } else {
+      int growth = current_length * (growth_factor - 1);
+      if (growth > max_growth) {
+        growth = max_growth;
+      }
+      new_capacity = current_length + growth;
+      if (new_capacity < min_capacity) {
+        new_capacity = min_capacity + growth;
+      }
     }
     Vector<T> new_chunk = Vector<T>::New(new_capacity);
     int new_index = PrepareGrow(new_chunk);