Makes it so we don't start watchdog when running under debugger

There is nothing worse than stepping through the debugger and suddenly
hitting the watchdog timer DCHECK. If you're running under a debugger
seems like you don't care about the watchdog thread. So, make it so we
don't start watchdog in this case.

BUG=none
TEST=none
R=rtenneti@chromium.org

Review URL: https://codereview.chromium.org/573683003

Cr-Commit-Position: refs/heads/master@{#297071}

chrome/browser/chrome_browser_main.cc

@@ -1082,9 +1082,11 @@ int ChromeBrowserMainParts::PreMainMessageLoopRunImpl() {
   StartMetricsRecording();
 #endif
 
-  // Create watchdog thread after creating all other threads because it will
-  // watch the other threads and they must be running.
-  browser_process_->watchdog_thread();
+  if (!base::debug::BeingDebugged()) {
+    // Create watchdog thread after creating all other threads because it will
+    // watch the other threads and they must be running.
+    browser_process_->watchdog_thread();
+  }
 
   // Do any initializating in the browser process that requires all threads
   // running.