Refactoring: replace NULL by nullptr for pointers (3rd CL).

This CL mainly handles passing/returning NULL to/from a function.

BUG=angleproject:2001

Change-Id: I34802f792e710e3d7ff697cbe4701dc1bf5ab009
Reviewed-on: https://chromium-review.googlesource.com/485060
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/compiler/translator/Compiler.cpp b/src/compiler/translator/Compiler.cpp
index e1edaaa..51398f5 100644
--- a/src/compiler/translator/Compiler.cpp
+++ b/src/compiler/translator/Compiler.cpp
@@ -144,7 +144,7 @@
     }
     ~TScopedPoolAllocator()
     {
-        SetGlobalPoolAllocator(NULL);
+        SetGlobalPoolAllocator(nullptr);
         mAllocator->pop();
     }
 
@@ -199,7 +199,7 @@
 
 TShHandleBase::~TShHandleBase()
 {
-    SetGlobalPoolAllocator(NULL);
+    SetGlobalPoolAllocator(nullptr);
     allocator.popAll();
 }
 
@@ -216,7 +216,7 @@
       clampingStrategy(SH_CLAMP_WITH_CLAMP_INTRINSIC),
       builtInFunctionEmulator(),
       mDiagnostics(infoSink.info),
-      mSourcePath(NULL),
+      mSourcePath(nullptr),
       mComputeShaderLocalSizeDeclared(false),
       mTemporaryIndex(0)
 {
@@ -479,7 +479,7 @@
     if (success)
         return root;
 
-    return NULL;
+    return nullptr;
 }
 
 bool TCompiler::compile(const char *const shaderStrings[],