Add sk_careful_memcpy to catch undefined behavior in memcpy.

include/core/SkTDArray.h

Index: include/core/SkTDArray.h
diff --git a/include/core/SkTDArray.h b/include/core/SkTDArray.h
index 26c6c7f8956b6cb1cdd80eaad35af7ee774f47bd..381eb1ae0e67e3cfb099009556724c1eda3cd29d 100644
--- a/include/core/SkTDArray.h
+++ b/include/core/SkTDArray.h
@@ -44,7 +44,7 @@ public:
             if (src.fCount > fReserve) {
                 SkTDArray<T> tmp(src.fArray, src.fCount);
                 this->swap(tmp);
-            } else {
+            } else if (src.fArray) {

[tomhudson, 2015/12/08 16:31:40]

Do we not need to invalidate the current contents of this if !src.fArray?
(fCount = 0, maybe?)

                 memcpy(fArray, src.fArray, sizeof(T) * src.fCount);
                 fCount = src.fCount;
             }