Factor out snapshot helpers from main.cc.

runtime/bin/bin.gypi

Index: runtime/bin/bin.gypi
diff --git a/runtime/bin/bin.gypi b/runtime/bin/bin.gypi
index be196cf71cf31bf186ba59e9d9829f9ad0dc5114..3119ce0da94f1e746ef639b5aee2b2d4c7a4deeb 100644
--- a/runtime/bin/bin.gypi
+++ b/runtime/bin/bin.gypi
@@ -1122,12 +1122,16 @@
         '../../third_party/', # Zlib
       ],
       'sources': [
-        'main.cc',
         'builtin.h',
         'builtin_common.cc',
         'builtin_natives.cc',
         'builtin_nolib.cc',
+        'error_exit.cc',
+        'error_exit.h',
         'io_natives.h',
+        'main.cc',
+        'snapshot_utils.cc',
+        'snapshot_utils.h',
         'vmservice_impl.cc',
         'vmservice_impl.h',
         '<(observatory_assets_cc_file)',
@@ -1181,13 +1185,17 @@
         '../../third_party/', # Zlib
       ],
       'sources': [
-        'main.cc',
         'builtin.h',
         'builtin_common.cc',
         'builtin_natives.cc',
         'builtin_nolib.cc',
+        'error_exit.cc',
+        'error_exit.h',
         'io_natives.h',
+        'main.cc',
         'snapshot_empty.cc',
+        'snapshot_utils.cc',
+        'snapshot_utils.h',
         'vmservice_impl.cc',
         'vmservice_impl.h',
         '<(observatory_assets_cc_file)',
@@ -1227,14 +1235,18 @@
         '..',
       ],
       'sources': [
-        'main.cc',
         'builtin.cc',
         'builtin.h',
         'builtin_common.cc',
         'builtin_natives.cc',
+        'error_exit.cc',
+        'error_exit.h',
         'io_natives.h',
+        'main.cc',
         'observatory_assets_empty.cc',
         'snapshot_empty.cc',
+        'snapshot_utils.cc',
+        'snapshot_utils.h',
         'vmservice_impl.cc',
         'vmservice_impl.h',
         # Include generated source files.