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

base/debug/dump_without_crashing.cc

Index: base/debug/dump_without_crashing.cc
diff --git a/base/debug/dump_without_crashing.cc b/base/debug/dump_without_crashing.cc
index 47fd873c19fd084c51d5e48455db040269ca47b3..4b338ca2930b69d110fd545176029aec75f9cd4a 100644
--- a/base/debug/dump_without_crashing.cc
+++ b/base/debug/dump_without_crashing.cc
@@ -18,9 +18,12 @@ namespace base {
 
 namespace debug {
 
-void DumpWithoutCrashing() {
-  if (dump_without_crashing_function_)
+bool DumpWithoutCrashing() {
+  if (dump_without_crashing_function_) {
     (*dump_without_crashing_function_)();
+    return true;
+  }
+  return false;
 }
 
 void SetDumpWithoutCrashingFunction(void (CDECL *function)()) {