Code refactoring: replace NULL by nullptr for pointers.

This is the frist change to replace NULL by nullptr.
It handles the initialization and assignment for pointers.

BUG=angleproject:2001

Change-Id: I6d4bb198a72e38b867cd2f65a6e6f2f61339a0b5
Reviewed-on: https://chromium-review.googlesource.com/481600
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/tests/gl_tests/BufferDataTest.cpp b/src/tests/gl_tests/BufferDataTest.cpp
index 5ba705d..8a821fd 100644
--- a/src/tests/gl_tests/BufferDataTest.cpp
+++ b/src/tests/gl_tests/BufferDataTest.cpp
@@ -148,7 +148,7 @@
 
     GLsizei allocSize = std::numeric_limits<GLsizei>::max() >> 2;
 
-    uint8_t *data = NULL;
+    uint8_t *data = nullptr;
     while (data == NULL && allocSize >= 4)
     {
         data = new (std::nothrow) uint8_t[allocSize];