Make LOG(FATAL) use IMMEDIATE_CRASH on official builds.

Use IMMEDIATE_CRASH on official builds instead of BreakDebugger in
LOG(CRASH), to try to increase the likelihood that stack unwinding will
work correctly. BreakDebugger isn't guaranteed to have a stack frame and
thus can thwart CFI unwinding.

This matches the behaviour of CHECK() so should be pretty safe.

Bug: 851851
Change-Id: I7bcf8669ee90aa3fe42769e4e4cc841bf1df1b57
Reviewed-on: https://chromium-review.googlesource.com/1147474Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577541}

base/logging.cc

@@ -852,7 +852,11 @@ LogMessage::~LogMessage() {
       }
 #endif
       // Crash the process to generate a dump.
+#if defined(OFFICIAL_BUILD) && defined(NDEBUG)
+      IMMEDIATE_CRASH();
+#else
       base::debug::BreakDebugger();
+#endif
     }
   }
 }