Implement --omit, --raw_[context_]file=... for mksnapshot tool.

These switches are analogous to --omit and --raw for js2c.py.
The goal it to allow embedders to externally load all (or generate) the V8 startup data.

There's a bit of gratuitous refactoring with the writing logic that helped me understand the code. Let me know if it's not an improvement.

BUG=355539
LOG=N
R=jochen@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/249283002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20941 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -653,7 +653,13 @@ DEFINE_string(testing_serialization_file, "/tmp/serdes",
 
 // mksnapshot.cc
 DEFINE_string(extra_code, NULL, "A filename with extra code to be included in"
-                  " the snapshot (mksnapshot only)")
+                                " the snapshot (mksnapshot only)")
+DEFINE_string(raw_file, NULL, "A file to write the raw snapshot bytes to. "
+                              "(mksnapshot only)")
+DEFINE_string(raw_context_file, NULL, "A file to write the raw context "
+                                      "snapshot bytes to. (mksnapshot only)")
+DEFINE_bool(omit, false, "Omit raw snapshot bytes in generated code. "
+                         "(mksnapshot only)")
 
 // code-stubs-hydrogen.cc
 DEFINE_bool(profile_hydrogen_code_stub_compilation, false,

src/serialize.h

@@ -464,7 +464,7 @@ class Serializer : public SerializerDeserializer {
   void VisitPointers(Object** start, Object** end);
   // You can call this after serialization to find out how much space was used
   // in each space.
-  int CurrentAllocationAddress(int space) {
+  int CurrentAllocationAddress(int space) const {
     ASSERT(space < kNumberOfSpaces);
     return fullness_[space];
   }