Remove duplicated heap allocation functions.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 573c5129f7a5d7a89d4fa285642882816313454f..18355f36024da8c9ae7b572588cbf569bc893706 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -864,14 +864,9 @@ class Heap {
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
-  MUST_USE_RESULT MaybeObject* AllocateByteArray(int length,
-                                                 PretenureFlag pretenure);
-
-  // Allocate a non-tenured byte array of the specified length
-  // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
-  // failed.
-  // Please note this does not perform a garbage collection.
-  MUST_USE_RESULT MaybeObject* AllocateByteArray(int length);
+  MUST_USE_RESULT MaybeObject* AllocateByteArray(
+      int length,
+      PretenureFlag pretenure  = NOT_TENURED);
 
   // Allocates an external array of the specified length and type.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
@@ -912,10 +907,9 @@ class Heap {
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
-  MUST_USE_RESULT MaybeObject* AllocateFixedArray(int length,
-                                                  PretenureFlag pretenure);
-  // Allocates a fixed array initialized with undefined values
-  MUST_USE_RESULT MaybeObject* AllocateFixedArray(int length);
+  MUST_USE_RESULT MaybeObject* AllocateFixedArray(
+      int length,
+      PretenureFlag pretenure = NOT_TENURED);
 
   // Allocates an uninitialized fixed array. It must be filled by the caller.
   //
@@ -1044,10 +1038,7 @@ class Heap {
 
   // Allocated a HeapNumber from value.
   MUST_USE_RESULT MaybeObject* AllocateHeapNumber(
-      double value,
-      PretenureFlag pretenure);
-  // pretenure = NOT_TENURED
-  MUST_USE_RESULT MaybeObject* AllocateHeapNumber(double value);
+      double value, PretenureFlag pretenure = NOT_TENURED);
 
   // Converts an int into either a Smi or a HeapNumber object.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation