Get headless_shell building on Windows.

headless/lib/headless_content_main_delegate.cc

Index: headless/lib/headless_content_main_delegate.cc
diff --git a/headless/lib/headless_content_main_delegate.cc b/headless/lib/headless_content_main_delegate.cc
index fc8f645164aacac9e20166366681351c0b52b680..77fd46bbd175bbeff2d5fc34ed6e532cdb5c3d12 100644
--- a/headless/lib/headless_content_main_delegate.cc
+++ b/headless/lib/headless_content_main_delegate.cc
@@ -201,7 +201,9 @@ void HeadlessContentMainDelegate::ZygoteForked() {
   // Unconditionally try to turn on crash reporting since we do not have access
   // to the latest browser options at this point when testing. Breakpad will
   // bail out gracefully if the browser process hasn't enabled crash reporting.
+#if defined(HEADLESS_USE_BREAKPAD)
   breakpad::InitCrashReporter(process_type);
+#endif
 }
 
 // static