Disable --write-protect-code-memory by default.

R=hablich@chromium.org
BUG=v8:6792,v8:7272,chromium:793428

Change-Id: Idcb3d8c5193ce943dc67e2275b89603563f131ca
Reviewed-on: https://chromium-review.googlesource.com/883509Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50838}

src/flag-definitions.h

@@ -640,7 +640,7 @@ DEFINE_BOOL(incremental_marking_wrappers, true,
             "use incremental marking for marking wrappers")
 DEFINE_BOOL(parallel_scavenge, true, "parallel scavenge")
 DEFINE_BOOL(trace_parallel_scavenge, false, "trace parallel scavenge")
-DEFINE_BOOL(write_protect_code_memory, true, "write protect code memory")
+DEFINE_BOOL(write_protect_code_memory, false, "write protect code memory")
 #ifdef V8_CONCURRENT_MARKING
 #define V8_CONCURRENT_MARKING_BOOL true
 #else