[logging] Reduce FailureMessage buffer size

This should reduce the probability of running out of stack space while logging
a fatal error message.
Additionally this CL distinguishes the error OOM error message when there is no
isolate available on the background thread.

Bug: chromium:839166
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I17e929f322dda20127fbf86a6154af5460e53490
Reviewed-on: https://chromium-review.googlesource.com/1041964Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52958}

src/api.cc

@@ -350,7 +350,9 @@ void i::V8::FatalProcessOutOfMemory(i::Isolate* isolate, const char* location,
     memset(&heap_stats, 0xBADC0DE, sizeof(heap_stats));
     // Note that the embedder's oom handler won't be called in this case. We
     // just crash.
-    FATAL("API fatal error handler returned after process out of memory");
+    FATAL(
+        "API fatal error handler returned after process out of memory on the "
+        "background thread");
     UNREACHABLE();
   }
 

src/base/logging.cc

@@ -135,7 +135,7 @@ class FailureMessage {
 
   static const uintptr_t kStartMarker = 0xdecade10;
   static const uintptr_t kEndMarker = 0xdecade11;
-  static const int kMessageBufferSize = 1024;
+  static const int kMessageBufferSize = 512;
 
   uintptr_t start_marker_ = kStartMarker;
   char message_[kMessageBufferSize];
@@ -154,6 +154,7 @@ void V8_Fatal(const char* file, int line, const char* format, ...) {
 
   fflush(stdout);
   fflush(stderr);
+  // Print the formatted message to stdout without cropping the output.
   v8::base::OS::PrintError("\n\n#\n# Fatal error in %s, line %d\n# ", file,
                            line);