Add support for saving VM state when a test fails.

bin/cros_run_vm_test

Index: bin/cros_run_vm_test
diff --git a/bin/cros_run_vm_test b/bin/cros_run_vm_test
index d62a2b98524fadc489971677df2df893e1be18bc..d6aa81a1303d37de2e475ff68e23786e01e3627d 100755
--- a/bin/cros_run_vm_test
+++ b/bin/cros_run_vm_test
@@ -18,6 +18,10 @@ DEFINE_string board "$DEFAULT_BOARD" \
     "The board for which you built autotest." b
 DEFINE_string image_path "" "Full path of the VM image"
 DEFINE_string results_dir_root "" "alternate root results directory"
+DEFINE_boolean save_vm_state ${FLAGS_FALSE} \
+    "Save the state of the VM when a test fails"
+DEFINE_string save_vm_state_file ${DEFAULT_QEMU_COW_IMAGE} \
+    "Name of file to save VM state into if test fails"
 DEFINE_string test_case "" "Name of the test case to run"
 DEFINE_boolean use_emerged ${FLAGS_FALSE} \
     "Force use of emerged autotest packages"
@@ -54,6 +58,16 @@ if [ -z "${FLAGS_test_case}" ] && [ -z "${FLAGS_ARGV}" ]; then
   die "You must specify a test case."
 fi
 
+if [ ${FLAGS_save_vm_state} -eq ${FLAGS_TRUE} ] &&
+   [ ${FLAGS_snapshot} -eq ${FLAGS_TRUE} ]; then
+  die "You cannot set both --snapshot and --save_vm_state."
+fi
+
+if [ ${FLAGS_save_vm_state} -eq ${FLAGS_TRUE} ] &&
+   [ -z ${FLAGS_save_vm_state_file} ]; then
+  die "You must specify a save_vm_state_file."
+fi
+
 USE_EMERGED=
 if [[ ${FLAGS_use_emerged} -eq ${FLAGS_TRUE} ]]; then
   USE_EMERGED="--use_emerged"
@@ -65,6 +79,15 @@ for test in ${FLAGS_ARGV}; do
   tests=( "${tests[@]}" "$(remove_quotes "${test}")" )
 done
 
+# Create a copy-on-write qcow2 file that is based off the default QEMU image
+# so that we can save state information into it.
+if [ ${FLAGS_save_vm_state} -eq ${FLAGS_TRUE} ]; then
+  QEMU_COW_IMAGE="$(${SCRIPTS_DIR}/get_latest_image.sh \
+      --board=${FLAGS_board})/${FLAGS_save_vm_state_file}"
+  qemu-img create -f qcow2 -b ${LATEST_IMAGE} ${QEMU_COW_IMAGE}
+  FLAGS_image_path=${QEMU_COW_IMAGE}
+fi
+
 trap stop_kvm EXIT
 start_kvm "${FLAGS_image_path}"
 info "Checking for ssh access to virtual machine."