Implement Dump-on-DCHECK (via alternate DCHECK and DCHECK_OP macro implementations).

third_party/WebKit/Source/wtf/Assertions.h

Index: third_party/WebKit/Source/wtf/Assertions.h
diff --git a/third_party/WebKit/Source/wtf/Assertions.h b/third_party/WebKit/Source/wtf/Assertions.h
index 4f9b24e207fa15ac027127735d79f10fbdd3ae06..f1f1004a851b26879660f1e320ea04e922ef5239 100644
--- a/third_party/WebKit/Source/wtf/Assertions.h
+++ b/third_party/WebKit/Source/wtf/Assertions.h
@@ -134,9 +134,17 @@ class WTF_EXPORT ScopedLogger {
 #undef ASSERT
 #endif
 
-#define DCHECK_AT(assertion, file, line)                            \
-  LAZY_STREAM(logging::LogMessage(file, line, #assertion).stream(), \
+#if defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+// In dump-on-DCHECK builds there is no log message, but |file| and |line must
+// still be referenced, so log them; the dump-on-DCHECK impl will not actually
+// log them.
+// See crbug.com/596231.
+#define DCHECK_AT(assertion, file, line) DCHECK(assertion) << file << line
+#else
+#define DCHECK_AT(assertion, file, line)                                     \
+  LAZY_STREAM(logging::LogMessage(file, line, logging::LOG_DCHECK).stream(), \
               DCHECK_IS_ON() ? !(assertion) : false)
+#endif
 
 #if DCHECK_IS_ON()
 #define ASSERT(assertion) DCHECK(assertion)