Fixed two register allocator bugs (off-by-one error/failure propagation).

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 757ae1c768d1496e96ad032c8a53dde61a1a322f..f04a462fd6c694a1840cae16dd112f48fe00e28d 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -668,8 +668,12 @@ LInstruction* LChunkBuilder::AssignPointerMap(LInstruction* instr) {
 LUnallocated* LChunkBuilder::TempRegister() {
   LUnallocated* operand =
       new(zone()) LUnallocated(LUnallocated::MUST_HAVE_REGISTER);
-  operand->set_virtual_register(allocator_->GetVirtualRegister());
-  if (!allocator_->AllocationOk()) Abort("Not enough virtual registers.");
+  int vreg = allocator_->GetVirtualRegister();
+  if (!allocator_->AllocationOk()) {
+    Abort("Out of virtual registers while trying to allocate temp register.");
+    return NULL;
+  }
+  operand->set_virtual_register(vreg);
   return operand;
 }