headless: Add support for minidump generation on Linux

headless/app/headless_shell_switches.cc

Index: headless/app/headless_shell_switches.cc
diff --git a/headless/app/headless_shell_switches.cc b/headless/app/headless_shell_switches.cc
index 06750596296047d2928b8986c97e7fcd47735b85..f20a60657f77c388713a5828ba428fe600e2d35a 100644
--- a/headless/app/headless_shell_switches.cc
+++ b/headless/app/headless_shell_switches.cc
@@ -7,6 +7,9 @@
 namespace headless {
 namespace switches {
 
+// The directory breakpad should store minidumps in.
+const char kCrashDumpsDir[] = "crash-dumps-dir";
+
 // Instructs headless_shell to cause network fetches to complete in order of
 // creation. This removes a significant source of network related
 // non-determinism at the cost of slower page loads.