Activate preserving of optimized code map accross GCs.

This enables --noflush-optimized-code-cache which allows preserving
entries in the optimized code map accross GCs. This only applies to
values being reachable through other paths.

R=hpayer@chromium.org,hablich@chromium.org

Review URL: https://codereview.chromium.org/1217863006

Cr-Commit-Position: refs/heads/master@{#29755}

src/flag-definitions.h

@@ -358,7 +358,7 @@ DEFINE_BOOL(lookup_sample_by_shared, true,
             "when picking a function to optimize, watch for shared function "
             "info, not JSFunction itself")
 DEFINE_BOOL(cache_optimized_code, true, "cache optimized code for closures")
-DEFINE_BOOL(flush_optimized_code_cache, true,
+DEFINE_BOOL(flush_optimized_code_cache, false,
             "flushes the cache of optimized code for closures on every GC")
 DEFINE_BOOL(inline_construct, true, "inline constructor calls")
 DEFINE_BOOL(inline_arguments, true, "inline functions with arguments object")