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

base/logging.cc

Index: base/logging.cc
diff --git a/base/logging.cc b/base/logging.cc
index cea6edae4a37cef2519ff32045c46c0a3c73e4d0..15ab4735b7114ed2c60585e3109e340027b744d1 100644
--- a/base/logging.cc
+++ b/base/logging.cc
@@ -57,6 +57,7 @@ typedef pthread_mutex_t* MutexHandle;
 #include "base/command_line.h"
 #include "base/debug/alias.h"
 #include "base/debug/debugger.h"
+#include "base/debug/dump_without_crashing.h"
 #include "base/debug/stack_trace.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/string_piece.h"
@@ -82,8 +83,10 @@ namespace {
 VlogInfo* g_vlog_info = nullptr;
 VlogInfo* g_vlog_info_prev = nullptr;
 
-const char* const log_severity_names[LOG_NUM_SEVERITIES] = {
-  "INFO", "WARNING", "ERROR", "FATAL" };
+const char* const log_severity_names[] = {"INFO", "WARNING", "ERROR", "FATAL",
+                                          "DUMP"};
+static_assert(LOG_NUM_SEVERITIES == arraysize(log_severity_names),
+              "Incorrect number of log_severity_names");
 
 const char* log_severity_name(int severity) {
   if (severity >= 0 && severity < LOG_NUM_SEVERITIES)
@@ -123,6 +126,7 @@ bool show_error_dialogs = false;
 // An assert handler override specified by the client to be called instead of
 // the debug message dialog and process termination.
 LogAssertHandlerFunction log_assert_handler = nullptr;
+
 // A log message handler that gets notified of every log message we process.
 LogMessageHandlerFunction log_message_handler = nullptr;
 
@@ -726,7 +730,7 @@ LogMessage::~LogMessage() {
     }
   }
 
-  if (severity_ == LOG_FATAL) {
+  if (severity_ == LOG_FATAL || severity_ == LOG_DUMP) {
     // Write the log message to the global activity tracker, if running.
     base::debug::GlobalActivityTracker* tracker =
         base::debug::GlobalActivityTracker::Get();
@@ -739,7 +743,20 @@ LogMessage::~LogMessage() {
     str_newline.copy(str_stack, arraysize(str_stack));
     base::debug::Alias(str_stack);
 
-    if (log_assert_handler) {
+    if (severity_ == LOG_DUMP) {
+      // To ensure we don't risk spamming Crash with dump-on-DCHECK reports we
+      // log
+      // only the first[*] DCHECK to fail once DumpWithoutCrashing() is working.
+      // [*] This is racey, but in the pathological case still only results in
+      // one
+      // dump per-racing-thread, rather than our aim of one per-process.
+      static bool dump_on_dcheck = true;

[Wez, 2017/01/15 01:18:41]

gab, danakj: Perhaps this should be a global so we can provide a
ResetDumpOnDCheckForTest(), so it's safe to run multiple-DUMP tests in a single
process; except right now we only have a single test. WDYT?

+      if (dump_on_dcheck)
+        dump_on_dcheck = !base::debug::DumpWithoutCrashing();
+      return;
+    }
+
+    else if (log_assert_handler) {
       // Make a copy of the string for the handler out of paranoia.
       log_assert_handler(std::string(stream_.str()));
     } else {