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/DrawProfiler.cpp b/libs/hwui/DrawProfiler.cpp
index e590642..ecde5ff 100644
--- a/libs/hwui/DrawProfiler.cpp
+++ b/libs/hwui/DrawProfiler.cpp
@@ -59,7 +59,7 @@
 DrawProfiler::DrawProfiler()
         : mType(kNone)
         , mDensity(0)
-        , mData(NULL)
+        , mData(nullptr)
         , mDataSize(0)
         , mCurrentFrame(-1)
         , mPreviousTime(0)
@@ -160,7 +160,7 @@
 
 void DrawProfiler::destroyData() {
     delete mData;
-    mData = NULL;
+    mData = nullptr;
 }
 
 void DrawProfiler::addRect(Rect& r, float data, float* shapeOutput) {