Add overrides and switch to nullptr keyword for all files

Adds remaining missing overrides and nullptr usages, missed due to
an extreme failure in tool usage.

Change-Id: I56abd72975a3999ad13330003c348db40f59aebf
diff --git a/libs/hwui/AnimationContext.cpp b/libs/hwui/AnimationContext.cpp
index a20bdae..097be08 100644
--- a/libs/hwui/AnimationContext.cpp
+++ b/libs/hwui/AnimationContext.cpp
@@ -59,7 +59,7 @@
             "Missed running animations last frame!");
     AnimationHandle* head = mNextFrameAnimations.mNextHandle;
     if (head) {
-        mNextFrameAnimations.mNextHandle = NULL;
+        mNextFrameAnimations.mNextHandle = nullptr;
         mCurrentFrameAnimations.mNextHandle = head;
         head->mPreviousHandle = &mCurrentFrameAnimations;
     }
@@ -84,15 +84,15 @@
 
 AnimationHandle::AnimationHandle(AnimationContext& context)
         : mContext(context)
-        , mPreviousHandle(NULL)
-        , mNextHandle(NULL) {
+        , mPreviousHandle(nullptr)
+        , mNextHandle(nullptr) {
 }
 
 AnimationHandle::AnimationHandle(RenderNode& animatingNode, AnimationContext& context)
         : mRenderNode(&animatingNode)
         , mContext(context)
-        , mPreviousHandle(NULL)
-        , mNextHandle(NULL) {
+        , mPreviousHandle(nullptr)
+        , mNextHandle(nullptr) {
     mRenderNode->animators().setAnimationHandle(this);
 }
 
@@ -114,7 +114,7 @@
     LOG_ALWAYS_FATAL_IF(mRenderNode->animators().hasAnimators(),
             "Releasing the handle for an RenderNode with outstanding animators!");
     removeFromList();
-    mRenderNode->animators().setAnimationHandle(NULL);
+    mRenderNode->animators().setAnimationHandle(nullptr);
     delete this;
 }
 
@@ -135,8 +135,8 @@
     if (mNextHandle) {
         mNextHandle->mPreviousHandle = mPreviousHandle;
     }
-    mPreviousHandle = NULL;
-    mNextHandle = NULL;
+    mPreviousHandle = nullptr;
+    mNextHandle = nullptr;
 }
 
 } /* namespace uirenderer */