More consistently use auto for emit*, nullptr in asm code.

src/assembler.cpp

Index: src/assembler.cpp
diff --git a/src/assembler.cpp b/src/assembler.cpp
index 6099d71528e57f2de840c178a5b3e757bc4b0fd2..50d82b73ff2cda99e099366c4f89ff10b8c586ae 100644
--- a/src/assembler.cpp
+++ b/src/assembler.cpp
@@ -74,10 +74,10 @@ AssemblerBuffer::AssemblerBuffer(Assembler &assembler) : assembler_(assembler) {
 
 AssemblerBuffer::~AssemblerBuffer() {}
 
-// Returns the latest fixup at or after the given position, or NULL if
+// Returns the latest fixup at or after the given position, or nullptr if
 // there is none.  Assumes fixups were added in increasing order.
 AssemblerFixup *AssemblerBuffer::GetLatestFixup(intptr_t position) const {
-  AssemblerFixup *latest_fixup = NULL;
+  AssemblerFixup *latest_fixup = nullptr;
   for (auto I = fixups_.rbegin(), E = fixups_.rend(); I != E; ++I) {
     if ((*I)->position() < position)
       return latest_fixup;