add release-mode checks for null, at least for a while

src/core/SkPaint.cpp

Index: src/core/SkPaint.cpp
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index 0e34be6db8266f9f5cd45d349d1e96fad4945cd2..88e5b432eb8d714bb4ae52d716844d22f01e537a 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -107,6 +107,11 @@ SkPaint::SkPaint() {
 }
 
 SkPaint::SkPaint(const SkPaint& src) {
+    // Diagnoistic. May remove later. See crbug.com/364224
+    if (NULL == &src) {
+        sk_throw();
+    }
+
 #define COPY(field) field = src.field
 #define REF_COPY(field) field = SkSafeRef(src.field)