Remove 6 unused flags.

src/flag-definitions.h

Index: src/flag-definitions.h
===================================================================
--- src/flag-definitions.h	(revision 10644)
+++ src/flag-definitions.h	(working copy)
@@ -133,12 +133,10 @@
 DEFINE_bool(crankshaft, true, "use crankshaft")
 DEFINE_string(hydrogen_filter, "", "hydrogen use/trace filter")
 DEFINE_bool(use_range, true, "use hydrogen range analysis")
-DEFINE_bool(eliminate_dead_phis, true, "eliminate dead phis")
 DEFINE_bool(use_gvn, true, "use hydrogen global value numbering")
 DEFINE_bool(use_canonicalizing, true, "use hydrogen instruction canonicalizing")
 DEFINE_bool(use_inlining, true, "use function inlining")
 DEFINE_bool(limit_inlining, true, "limit code size growth from inlining")
-DEFINE_bool(eliminate_empty_blocks, true, "eliminate empty blocks")
 DEFINE_bool(loop_invariant_code_motion, true, "loop invariant code motion")
 DEFINE_bool(collect_megamorphic_maps_from_stub_cache,
             true,
@@ -301,8 +299,6 @@
 DEFINE_bool(always_compact, false, "Perform compaction on every full GC")
 DEFINE_bool(lazy_sweeping, true,
             "Use lazy sweeping for old pointer and data spaces")
-DEFINE_bool(cleanup_caches_in_maps_at_gc, true,
-            "Flush code caches in maps during mark compact cycle.")
 DEFINE_bool(never_compact, false,
             "Never perform compaction on full GC - testing only")
 DEFINE_bool(compact_code_space, false,
@@ -314,14 +310,6 @@
            "Default seed for initializing random generator "
            "(0, the default, means to use system random).")
 
-DEFINE_bool(canonicalize_object_literal_maps, true,
-            "Canonicalize maps for object literals.")
-
-DEFINE_int(max_map_space_pages, MapSpace::kMaxMapPageIndex - 1,
-           "Maximum number of pages in map space which still allows to encode "
-           "forwarding pointers.  That's actually a constant, but it's useful "
-           "to control it with a flag for better testing.")
-
 // objects.cc
 DEFINE_bool(use_verbose_printer, true, "allows verbose printing")
 
@@ -471,10 +459,6 @@
 // runtime.cc
 DEFINE_bool(trace_lazy, false, "trace lazy compilation")
 
-// serialize.cc
-DEFINE_bool(debug_serialization, false,
-            "write debug information into the snapshot.")
-
 // spaces.cc
 DEFINE_bool(collect_heap_spill_statistics, false,
             "report heap spill statistics along with heap_stats "