Implement Dump-on-DCHECK (via a new LogSeverity).

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 db71532243b89a103a0bb64e8fd75fe840260266..fc4da7bfc1881745d359d65e4f447182815b7878 100644
--- a/third_party/WebKit/Source/wtf/Assertions.h
+++ b/third_party/WebKit/Source/wtf/Assertions.h
@@ -49,12 +49,7 @@
 // Users must test "#if ENABLE(ASSERT)", which helps ensure that code
 // testing this macro has included this header.
 #ifndef ENABLE_ASSERT
-#if defined(NDEBUG) && !defined(DCHECK_ALWAYS_ON)
-/* Disable ASSERT* macros in release mode by default. */
-#define ENABLE_ASSERT 0
-#else
-#define ENABLE_ASSERT 1
-#endif /* defined(NDEBUG) && !defined(DCHECK_ALWAYS_ON) */
+#define ENABLE_ASSERT DCHECK_IS_ON()
 #endif
 
 #ifndef LOG_DISABLED
@@ -157,6 +152,18 @@ class WTF_EXPORT ScopedLogger {
 #undef ASSERT
 #endif
 
+// If DCHECK is configured to dump-without-crashing then enable assertions,
+// but also configure them to dump-without-crashing.
+#if defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+
+#define ASSERT(assertion) DCHECK(assertion)
+#define ASSERT_NOT_REACHED() NOTREACHED()

[Wez, 2016/12/19 23:57:46]

Note that this has significant performance implications. Yay.

[esprehn, 2016/12/20 03:16:29]

What was the perf change? Not sure I understand how switching ASSERT_NOT_REACHED
changed the perf? Note that blink will probably switch all of these to
NOTREACHED() someday so it'd be good to understand what changed?

[Wez, 2017/01/07 00:18:47]

Earlier versions of the patch left Blink assertions disabled, to avoid the
related book-keeping overhead.

+
+// |file| and |line| won't actually be logged, but must be referenced.
+#define DCHECK_AT(assertion, file, line) DCHECK(assertion) << file << line
+
+#else  // defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+
 #define DCHECK_AT(assertion, file, line)                            \
   LAZY_STREAM(logging::LogMessage(file, line, #assertion).stream(), \
               DCHECK_IS_ON() ? !(assertion) : false)
@@ -182,6 +189,8 @@ class WTF_EXPORT ScopedLogger {
 
 #endif
 
+#endif  // defined(DCHECK_ALWAYS_ON)
+
 // Users must test "#if ENABLE(SECURITY_ASSERT)", which helps ensure
 // that code testing this macro has included this header.
 #if defined(ADDRESS_SANITIZER) || ENABLE(ASSERT)