ARM: Make use of d16-d31 when available.

src/lithium-allocator.cc

Index: src/lithium-allocator.cc
diff --git a/src/lithium-allocator.cc b/src/lithium-allocator.cc
index b23c86766a6fb71e86927aebefdd1b2034aab359..99dd874d20f262e476616558c442af3a4a9b7790 100644
--- a/src/lithium-allocator.cc
+++ b/src/lithium-allocator.cc
@@ -1509,7 +1509,7 @@ void LAllocator::AllocateRegisters() {
   ASSERT(inactive_live_ranges_.is_empty());
 
   if (mode_ == DOUBLE_REGISTERS) {
-    for (int i = 0; i < fixed_double_live_ranges_.length(); ++i) {
+    for (int i = 0; i < DoubleRegister::NumAllocatableRegisters(); ++i) {
       LiveRange* current = fixed_double_live_ranges_.at(i);
       if (current != NULL) {
         AddToInactive(current);