Replace NULL with nullptr

Also fixed some lines that were too long, and a few other minor
details.

Change-Id: I6efba5fb6e03eb5d0a300fddb2a75bf8e2f175cb
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index bef5896..6ab57b8 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -714,7 +714,7 @@
     // TODO: Implement static evaluation of long unary operations.
     //
     // Do not exit with a fatal condition here.  Instead, simply
-    // return `nullptr' to notify the caller that this instruction
+    // return `null' to notify the caller that this instruction
     // cannot (yet) be statically evaluated.
     return nullptr;
   }
@@ -750,7 +750,7 @@
 }
 
 // If `GetConstantRight()` returns one of the input, this returns the other
-// one. Otherwise it returns nullptr.
+// one. Otherwise it returns null.
 HInstruction* HBinaryOperation::GetLeastConstantLeft() const {
   HInstruction* most_constant_right = GetConstantRight();
   if (most_constant_right == nullptr) {